High-entropy high-nickel cobalt-free precursor, high-entropy high-nickel cobalt-free single-crystal positive electrode material, preparation method thereof, and lithium ion battery

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a high-entropy high-nickel cobalt-free precursor, a high-entropy high-nickel cobalt-free single-crystal positive electrode material and a preparation method thereof and a lithium ion battery. The high-entropy high-nickel cobalt-free precursor comprises a core layer and a high-entropy doped shell layer coated on at least part of the surface of the core layer; the core layer comprises a first nickel-manganese hydroxide; the high-entropy doped shell layer comprises a high-entropy doped second nickel-manganese hydroxide; and the doped elements in the high-entropy doped second nickel-manganese hydroxide include titanium, magnesium, aluminum, zirconium and molybdenum. The high-entropy high-nickel cobalt-free precursor provided by the application is coated with a high-entropy doped shell layer containing titanium, magnesium, aluminum, zirconium and molybdenum on the surface of the core layer containing the first nickel-manganese hydroxide, which is beneficial to reducing the exposure degree of {010} active crystal faces in the precursor, promoting the preferred growth of the positive electrode material along the (003) plane, and further improving the electrochemical performance and cycle stability of the high-entropy high-nickel cobalt-free single-crystal positive electrode material.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to high-entropy high-nickel cobalt-free precursors, high-entropy high-nickel cobalt-free single-crystal cathode materials and their preparation methods, and lithium-ion batteries. Background Technology

[0002] With the rapid development of new energy vehicles, large-scale energy storage devices, and portable electronic devices, the market has placed higher demands on the energy density of lithium-ion batteries. As a core component determining the energy density, cost, and safety of lithium batteries, the performance of the cathode material directly restricts the overall performance of the battery. Against this backdrop, high-nickel ternary cathode materials (LiNi) have become increasingly important. x Co y Mn 1-x- y O2 (x ≥ 0.8) has become one of the most promising cathode material systems due to its high specific capacity (≥200 mAh / g) and excellent energy density. Currently, high-nickel ternary cathode materials are rapidly evolving towards higher nickel content and single-crystal development. Single-crystal cathode materials with a nickel content exceeding 90% are expected to increase the energy density at the battery pack level to 350Wh / kg, meeting the needs of next-generation technologies such as solid-state batteries. Compared to polycrystalline materials, single-crystal high-nickel cathodes significantly enhance mechanical strength and structural integrity by eliminating internal grain boundaries, effectively preventing the generation of microcracks at grain boundaries and improving cycle life by more than 30%. Nevertheless, high-nickel single-crystal cathode materials still face challenges such as kinetic lag caused by the long lithium-ion diffusion distance and the lattice strain that accumulates continuously during charging and discharging. These problems severely restrict their large-scale industrialization.

[0003] Furthermore, cobalt (Co), as a key component in high-nickel ternary cathode materials, plays an irreplaceable role in maintaining the structural stability of the material and improving its electrochemical performance. For example, cobalt can alleviate the magnetoresistance effect in the transition metal layer and effectively suppress Ni. 2+ Migration to the lithium layer reduces Li + / Ni 2+ The degree of cation mixing is beneficial for maintaining the integrity of the layered ordered structure and ensuring the rapid diffusion channels of Li⁺. However, due to the scarcity and cost of cobalt, the development of high-nickel cobalt-free cathode materials has become an inevitable trend and key direction in the field of lithium-ion battery research.

[0004] However, completely removing cobalt results in high-nickel cobalt-free cathode materials facing problems such as deteriorated structural stability, increased interfacial instability, and more complex synthesis processes. For the structural layers, the absence of cobalt leads to... + / Ni 2+ The degree of cation mixing is significantly aggravated, severely hindering Li +The diffusion of [unspecified material] causes a reversible capacity decrease and a deterioration in rate performance. During the delithiation process, the magnetoresistance effect induced by unpaired electrons triggers severe lattice distortion, leading to intracrystalline microcracks and irreversible phase transitions. For the interface layer, the high-spin Ni [unspecified material] on the surface of the high-nickel, cobalt-free cathode material... 3+ Aggregation exacerbates interfacial chemical instability, triggers irreversible phase transitions and loss of active lithium, worsens particle surface stability, and makes them more susceptible to side reactions with the electrolyte. This severely limits the electrochemical performance and cycle stability of the cathode material.

[0005] The aforementioned problems can be alleviated through elemental doping or surface coating. For example, CN115763749A provides a composite-doped high-nickel large single-crystal ternary layered oxide cathode material, which includes a substrate and a coating layer disposed on the surface of the substrate. The substrate contains lithium nickel cobalt manganese oxide containing bulk flux and lattice stabilizer, and the coating layer contains surface dopants. This patent can obtain single-crystal particles with large particle size, stable overall structure, and uniform surface distribution by using multiple dopants, but it cannot precisely adjust the crystal structure of the cathode material, and the degree of improvement in structural stability and interface stability is still quite limited. Summary of the Invention

[0006] Based on this, the technical problem to be solved by this application is how to provide a high-entropy, high-nickel, cobalt-free precursor, a high-entropy, high-nickel, cobalt-free single-crystal cathode material and its preparation method, and a lithium-ion battery, so as to control the crystal structure of the cathode material, improve the structural stability and interface stability of the cathode material, and improve the electrochemical performance and cycle stability. In order to solve the above technical problem, the high-entropy, high-nickel, cobalt-free precursor provided by this application, by coating the surface of the core layer containing the first nickel manganese hydroxide with a high-entropy doped shell containing titanium, magnesium, aluminum, zirconium and molybdenum elements, is beneficial to reduce the exposure degree of the {010} active crystal plane in the precursor, promote the preferential growth of the cathode material along the (003) plane, thereby improving the electrochemical performance and cycle stability of the high-entropy, high-nickel, cobalt-free single-crystal cathode material, and improving the first efficiency and capacity retention of the battery.

[0007] In a first aspect, this application provides a high-entropy, high-nickel, cobalt-free precursor, comprising a core layer and a high-entropy doped shell layer covering at least a portion of the surface of the core layer;

[0008] The core layer comprises a first nickel-manganese hydroxide;

[0009] The high-entropy doped shell includes a high-entropy doped second nickel-manganese hydroxide; the doping elements in the high-entropy doped second nickel-manganese hydroxide include titanium, magnesium, aluminum, zirconium and molybdenum.

[0010] In some embodiments, the high-entropy, high-nickel, cobalt-free precursor satisfies one or more of the following characteristics:

[0011] (1) Based on a molar amount of nickel and manganese of 100 mol%, the nickel content in the first nickel-manganese hydroxide and the second nickel-manganese hydroxide is independently greater than or equal to 90 mol%, which can be selected as 90 mol% to 96 mol%;

[0012] (2) The molecular formula of the first nickel-manganese hydroxide is Ni a Mn 1-a (OH)2; where a≥0.9, optionally a is 0.9~0.96;

[0013] (3) The D50 of the core layer is 1.5 μm to 3 μm;

[0014] (4) Based on a molar amount of transition metal elements of 100 mol%, the doping amounts of titanium, magnesium, aluminum, zirconium and molybdenum in the high-entropy doped second nickel-manganese hydroxide are each 0.1 mol% to 2 mol%;

[0015] (5) The molecular formula of the high-entropy doped second nickel-manganese hydroxide is Ni b Mn 1-b-c1-c2-c3-c4- c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, c1, c2, c3, c4 and c5 are each independently 0.001~0.02; further optionally, a is 0.9~0.96;

[0016] (6) The thickness of the high-entropy doped shell is 0.25 μm to 1 μm.

[0017] Secondly, this application provides a method for preparing a high-entropy, high-nickel, cobalt-free precursor, comprising the following steps:

[0018] Provide a first nickel-manganese hydroxide to form a reaction solution containing the first nickel-manganese hydroxide;

[0019] Titanium salt, magnesium salt, aluminum salt, zirconium salt, molybdenum salt, nickel salt and manganese salt are first mixed to form a first mixture;

[0020] The first mixture is added to the reaction solution containing the first nickel-manganese hydroxide, and a first coprecipitation reaction is carried out to form a high-entropy doped shell of the target thickness on the surface of the first nickel-manganese hydroxide, thereby preparing the high-entropy, high-nickel, cobalt-free precursor.

[0021] In some embodiments, the preparation method satisfies one or more of the following characteristics:

[0022] (1) The titanium salt includes at least one of titanium oxysulfate and titanium sulfate;

[0023] (2) The magnesium salt includes magnesium sulfate;

[0024] (3) The aluminum salts include aluminum sulfate;

[0025] (4) The zircon salt includes zirconium sulfate;

[0026] (5) The molybdenum salt includes ammonium molybdate;

[0027] (6) The nickel salt includes nickel sulfate;

[0028] (7) The manganese salt includes manganese sulfate;

[0029] (8) With the molar amounts of nickel and manganese being 100 mol%, the nickel content in the first nickel-manganese hydroxide and the high-entropy doped shell is independently greater than or equal to 90 mol%, which can be selected as 90 mol% to 96 mol%.

[0030] (9) Based on a total molar amount of manganese and nickel of 100 mol%, the content of titanium, magnesium, aluminum, zirconium and molybdenum in the first mixture is 0.1 mol% to 2 mol%.

[0031] (10) The molecular formula of the first nickel-manganese hydroxide is Ni a Mn 1-a (OH)2; where a≥0.9, optionally a is 0.9~0.96;

[0032] (11) The D50 of the first nickel-manganese hydroxide is 1.5 μm to 3 μm;

[0033] (12) The target thickness is 0.25 μm to 1 μm;

[0034] (13) The high-entropy doped shell includes a high-entropy doped second nickel-manganese hydroxide with the molecular formula Ni b Mn 1-b-c1-c2-c3-c4-c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, c1, c2, c3, c4 and c5 are each independently 0.001~0.02; further optionally, a is 0.9~0.96.

[0035] In some embodiments, the conditions for the first coprecipitation reaction satisfy one or more of the following characteristics:

[0036] (1) The ammonia concentration is 7 g / L to 10 g / L;

[0037] (2) pH is 10.5~11;

[0038] (3) The stirring speed is 550 r / min to 650 r / min;

[0039] (4) The reaction temperature is 50℃~60℃.

[0040] Thirdly, this application provides a high-entropy, high-nickel, cobalt-free precursor prepared by the preparation method described in the second aspect.

[0041] Fourthly, this application provides a method for preparing a high-entropy, high-nickel, cobalt-free single-crystal cathode material, comprising the following steps:

[0042] The high-entropy, high-nickel, cobalt-free precursor described in the first or third aspect is mixed with a lithium salt and calcined in an oxygen-containing atmosphere to prepare the high-entropy, high-nickel, cobalt-free single-crystal cathode material.

[0043] In some embodiments, the preparation method satisfies one or more of the following characteristics:

[0044] (1) The molar ratio of lithium in the lithium salt to transition metal in the high-entropy, high-nickel, cobalt-free precursor is (1-1.1):1;

[0045] (2) The lithium salt includes at least one of lithium carbonate and lithium hydroxide;

[0046] (3) The calcination conditions include: performing the first calcination and the second calcination in sequence, with the temperature of the first calcination being 400℃~600℃ and the temperature of the second calcination being 795℃~895℃;

[0047] Optionally, the first calcination time is 2 hours to 8 hours;

[0048] Optionally, the second calcination time is 10h to 20h.

[0049] Fifthly, this application provides a high-entropy, high-nickel, cobalt-free single-crystal cathode material prepared by the preparation method of the high-entropy, high-nickel, cobalt-free single-crystal cathode material described in the fourth aspect;

[0050] Optionally, the high-entropy, high-nickel, cobalt-free single-crystal cathode material includes a core and a coating layer covering at least a portion of the surface of the core; the core includes lithium nickel manganese oxide; the coating layer includes high-entropy doped lithium nickel manganese oxide; the doping elements in the high-entropy doped lithium nickel manganese oxide include titanium, magnesium, aluminum, zirconium, and molybdenum;

[0051] Optionally, the molecular formula of the lithium nickel manganese oxide is LiNi. a Mn 1-a(OH)2; where a≥0.9, optionally a is 0.9~0.96;

[0052] Optionally, the high-entropy doped lithium nickel manganese oxide has the molecular formula LiNi. b Mn 1-b-c1-c2-c3-c4- c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, c1, c2, c3, c4 and c5 are each independently 0.001~0.02; further optionally, a is 0.9~0.96.

[0053] Sixthly, this application provides a lithium-ion battery, including a positive electrode sheet, wherein the positive electrode sheet includes a positive active material layer;

[0054] The positive electrode active material layer includes the high-nickel cobalt-free single-crystal positive electrode material described in the fifth aspect.

[0055] Compared with traditional technical solutions, the beneficial effects of this application are as follows:

[0056] 1. The high-entropy, high-nickel, cobalt-free precursor provided in this application, by coating the surface of the core layer containing a first nickel-manganese hydroxide with a high-entropy doped shell containing titanium, magnesium, aluminum, zirconium, and molybdenum, helps to reduce the exposure of the {010} active crystal plane in the precursor, promotes the preferential growth of the cathode material along the (003) plane, and thus improves the electrochemical performance and cycle stability of the high-entropy, high-nickel, cobalt-free single-crystal cathode material, improving the battery's first-time efficiency and capacity retention. Furthermore, this high-entropy doped shell forms a complex chemical bond network with high configurational entropy, significantly enhancing the transition metal-oxygen bond strength, thereby effectively suppressing anisotropic strain along the a / c axis during charging and discharging, reducing volume changes, eliminating microcrack generation at the source, and improving crystal mechanical integrity. Simultaneously, this shell can suppress irreversible surface reconstruction and electrolyte side reactions, promote the formation of a stable cathode-electrolyte interface film, expand the lithium layer spacing, reduce lithium-nickel mixing, and optimize lithium-ion diffusion kinetics, enabling the material to maintain high capacity even at high rates. In summary, this application successfully overcomes the trade-off between capacity and stability, achieving excellent long-cycle stability while maintaining high specific capacity.

[0057] 2. This application eliminates the dependence on cobalt, and has a natural advantage in adapting to higher nickel content and achieving higher energy density. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings are only for illustrating preferred embodiments and are not intended to limit this application. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0059] Figure 1 This is a schematic diagram of the high-entropy, high-nickel, cobalt-free precursor of this application.

[0060] Figure 2 This is a SEM image of the first nickel-manganese hydroxide NM9010-1.5μm, with a scale bar of 5μm.

[0061] Figure 3 This is a SEM image of the high-entropy, high-nickel, cobalt-free precursor NM9010-HE (core-shell) from Example 1, with a scale bar of 5 μm.

[0062] Figure 4 This is a SEM image of the first nickel-manganese hydroxide NM9010-2.5μm, with a scale bar of 5μm.

[0063] Figure 5 The image shows the XRD pattern of the first nickel manganese hydroxide NM9010-1.5μm, where I(100) / I(001) is 0.92.

[0064] Figure 6 The image shows the XRD pattern of the first nickel manganese hydroxide NM9010-2.5μm, where I(100) / I(001) is 0.67.

[0065] Figure 7 The image shows the XRD pattern of the high-entropy, high-nickel, cobalt-free precursor NM9010-HE (core-shell) from Example 1, where I(100) / I(001) is 0.47.

[0066] Figure 8 These are the XRD patterns of the cathode materials of Example 1 and Comparative Examples 1-2, where LNM9010-HE (core-shell) is Example 1, LNM9010-1.5 μm is Comparative Example 1, and LNM9010-2.5 μm is Comparative Example 2.

[0067] Figure 9 These are the 0.1C first-cycle charge-discharge curves of the batteries in Example 1 and Comparative Examples 1-2. Among them, LNM9010-HE (core-shell) is Example 1, LNM9010-1.5 μm is Comparative Example 1, and LNM9010-2.5 μm is Comparative Example 2.

[0068] Figure 10The results are the 1C cycle stability test results of the batteries of Example 1 and Comparative Examples 1 to 2. Among them, LNM9010-HE (core-shell) is Example 1, LNM9010-1.5 μm is Comparative Example 1, and LNM9010-2.5 μm is Comparative Example 2. Detailed Implementation

[0069] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0070] 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 in this application and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0071] In this application, "one or more" means any one, two or more of the listed items.

[0072] In this application, terms such as "first aspect" and "second aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first" and "second" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0073] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0074] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0075] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and liquid-liquid mixtures, and volume (molar) percentage for gas-gas mixtures.

[0076] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0077] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0078] Research has found that high-nickel single-crystal cathode materials still face challenges such as kinetic lag due to the long lithium-ion diffusion distance and lattice strain accumulating during charging and discharging. These problems severely restrict their large-scale industrialization. In particular, the complete removal of cobalt results in deteriorated structural stability, increased interfacial instability, and more complex synthesis processes for high-nickel cobalt-free cathode materials. While elemental doping or surface coating can alleviate these problems, traditional methods cannot precisely control the crystal structure of the cathode material, and the improvement in structural and interfacial stability remains quite limited.

[0079] In view of this, this application provides a high-entropy, high-nickel, cobalt-free precursor, a high-entropy, high-nickel, cobalt-free single-crystal cathode material and its preparation method, and a lithium-ion battery, so as to regulate the crystal structure of the cathode material, improve the structural stability and interface stability of the cathode material, and enhance the electrochemical performance and cycle stability.

[0080] In a first aspect, this application provides a high-entropy, high-nickel, cobalt-free precursor, comprising a core layer and a high-entropy doped shell layer covering at least a portion of the surface of the core layer;

[0081] The core layer comprises a first nickel-manganese hydroxide;

[0082] The high-entropy doped shell includes a high-entropy doped second nickel-manganese hydroxide; the doping elements in the high-entropy doped second nickel-manganese hydroxide include titanium, magnesium, aluminum, zirconium and molybdenum.

[0083] like Figure 1 As shown, the high-entropy, high-nickel, cobalt-free precursor of this application has an undoped nickel-manganese hydroxide core layer and a Ti, Mg, Al, Zr, and Mo high-entropy doped nickel-manganese hydroxide shell layer.

[0084] The high-entropy, high-nickel, cobalt-free precursor provided in this application, by coating the surface of the core layer containing a first nickel-manganese hydroxide with a high-entropy doped shell containing titanium, magnesium, aluminum, zirconium, and molybdenum, helps to reduce the exposure of the {010} active crystal plane in the precursor, promotes the preferential growth of the cathode material along the (003) plane, and thus improves the electrochemical performance and cycle stability of the high-entropy, high-nickel, cobalt-free single-crystal cathode material. Furthermore, this high-entropy doped shell forms a complex chemical bond network with high configurational entropy, significantly enhancing the transition metal-oxygen bond strength, thereby effectively suppressing anisotropic strain along the a / c axis during charging and discharging, reducing volume changes, eliminating the generation of microcracks from the source, and improving the mechanical integrity of the crystal. Simultaneously, this shell can suppress irreversible surface reconstruction and electrolyte side reactions, promote the formation of a stable cathode-electrolyte interface film, expand the lithium layer spacing, reduce lithium-nickel mixing, and optimize lithium-ion diffusion kinetics, enabling the material to maintain high capacity even at high rates. In summary, this application successfully overcomes the trade-off between capacity and stability, achieving excellent long-cycle stability while maintaining high specific capacity.

[0085] In some embodiments, with the molar amounts of nickel and manganese being 100 mol%, the nickel content in the first nickel-manganese hydroxide and the second nickel-manganese hydroxide is independently greater than or equal to 90 mol%, which can be selected as 90 mol% to 96 mol%, such as 90 mol%, 91 mol%, 92 mol%, 93 mol%, 94 mol%, 95 mol%, 96 mol%, etc.

[0086] In some embodiments, the molecular formula of the first nickel-manganese hydroxide is Ni a Mn 1-a (OH)2; where a≥0.9, optionally a is 0.9~0.96, for example 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96 etc.

[0087] In some embodiments, the D50 of the core layer is 1.5μm to 3μm, such as 1.5μm, 2μm, 2.5μm, 3μm, etc.

[0088] In some embodiments, with the molar amount of transition metal elements being 100 mol%, the doping amounts of titanium, magnesium, aluminum, zirconium, and molybdenum in the highly entropy-doped second nickel-manganese hydroxide are each independently 0.1 mol% to 2 mol%, for example, 0.1 mol%, 0.5 mol%, 0.8 mol%, 1 mol%, 1.2 mol%, 1.5 mol%, 1.8 mol%, 2 mol%, etc.

[0089] In some embodiments, the molecular formula of the high-entropy doped second nickel-manganese hydroxide is Ni b Mn 1-b-c1-c2-c3-c4-c5 Tic1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, and c1, c2, c3, c4 and c5 are each independently 0.001~0.02, for example 0.001, 0.005, 0.01, 0.15, 0.02, etc.; further optionally, a is 0.9~0.96, for example 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, etc.

[0090] In some embodiments, the thickness of the high-entropy doped shell is 0.25 μm to 1 μm, such as 0.25 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0091] Secondly, this application provides a method for preparing a high-entropy, high-nickel, cobalt-free precursor, comprising the following steps:

[0092] Provide a first nickel-manganese hydroxide to form a reaction solution containing the first nickel-manganese hydroxide;

[0093] Titanium salt, magnesium salt, aluminum salt, zirconium salt, molybdenum salt, nickel salt and manganese salt are first mixed to form a first mixture;

[0094] The first mixture is added to the reaction solution containing the first nickel-manganese hydroxide, and a first coprecipitation reaction is carried out to form a high-entropy doped shell of the target thickness on the surface of the first nickel-manganese hydroxide, thereby preparing the high-entropy, high-nickel, cobalt-free precursor.

[0095] The above preparation method can in situ coat the core layer containing the first nickel manganese hydroxide with a high-entropy doped shell containing titanium, magnesium, aluminum, zirconium and molybdenum elements, which is beneficial to reduce the exposure of the {010} active crystal plane in the precursor, promote the preferential growth of the cathode material along the (003) plane, and thus improve the electrochemical performance and cycle stability of the high-entropy high-nickel cobalt-free single crystal cathode material.

[0096] In some embodiments, the titanium salt includes at least one of titanium oxysulfate and titanium sulfate.

[0097] In some embodiments, the magnesium salt comprises magnesium sulfate; optionally, the magnesium sulfate comprises at least one of magnesium sulfate heptahydrate, magnesium sulfate monohydrate, and anhydrous magnesium sulfate.

[0098] In some embodiments, the aluminum salt comprises aluminum sulfate; optionally, the aluminum sulfate comprises at least one of aluminum sulfate octadecahydrate and anhydrous aluminum sulfate.

[0099] In some embodiments, the zirconium salt comprises zirconium sulfate; optionally, the zirconium sulfate comprises at least one of zirconium sulfate tetrahydrate and anhydrous zirconium sulfate.

[0100] In some embodiments, the molybdenum salt comprises ammonium molybdate; optionally, ammonium molybdate comprises at least one of ammonium molybdate tetrahydrate and anhydrous ammonium molybdate.

[0101] In some embodiments, the nickel salt comprises nickel sulfate; optionally, the nickel sulfate comprises at least one of nickel sulfate hexahydrate and anhydrous nickel sulfate.

[0102] In some embodiments, the manganese salt comprises manganese sulfate; alternatively, manganese sulfate comprises manganese sulfate monohydrate.

[0103] In some embodiments, with the molar amounts of nickel and manganese being 100 mol%, the nickel content in the first nickel-manganese hydroxide and the high-entropy doped shell is independently greater than or equal to 90 mol%, which can be selected as 90 mol% to 96 mol%, such as 90 mol%, 91 mol%, 92 mol%, 93 mol%, 94 mol%, 95 mol%, 96 mol%, etc.

[0104] In some embodiments, with the total molar amount of manganese and nickel being 100 mol%, the content of titanium, magnesium, aluminum, zirconium, and molybdenum in the first mixture is 0.1 mol% to 2 mol%, for example, 0.1 mol%, 0.5 mol%, 0.8 mol%, 1 mol%, 1.2 mol%, 1.5 mol%, 1.8 mol%, 2 mol%, etc.

[0105] In some embodiments, the molecular formula of the first nickel-manganese hydroxide is Ni a Mn 1-a (OH)2; where a≥0.9, optionally a is 0.9~0.96, for example 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96 etc.

[0106] In some embodiments, the D50 of the first nickel-manganese hydroxide is 1.5 μm to 3 μm, for example, 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc.

[0107] In some embodiments, the target thickness is 0.25μm to 1μm, such as 0.25μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, etc.

[0108] In some embodiments, the high-entropy doped shell comprises a high-entropy doped second nickel-manganese hydroxide with the molecular formula Ni b Mn1-b-c1-c2-c3-c4-c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, and c1, c2, c3, c4 and c5 are each independently 0.001~0.02, for example 0.001, 0.005, 0.01, 0.15, 0.02, etc.; further optionally, a is 0.9~0.96, for example 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, etc.

[0109] In some embodiments, the conditions for the first coprecipitation reaction satisfy one or more of the following characteristics:

[0110] (1) The ammonia concentration is 7g / L~10g / L, for example 7g / L, 8g / L, 9g / L, 10g / L, etc.;

[0111] (2) pH is 10.5~11, such as 10.5, 10.6, 10.7, 10.8, 10.9, 11, etc.;

[0112] (3) The stirring speed is 550 r / min to 650 r / min, for example, 550 r / min, 600 r / min, 650 r / min, etc.;

[0113] (4) The reaction temperature is 50℃~60℃, for example 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, etc.

[0114] In some embodiments, the total concentration of metal ions in the first mixture is 50 g / L to 200 g / L, for example, 50 g / L, 100 g / L, 150 g / L, 200 g / L, etc.

[0115] In some embodiments, the addition rate of the first mixture is 0.4 L / h to 0.8 L / h, for example, 0.4 L / h, 0.5 L / h, 0.6 L / h, 0.7 L / h, 0.8 L / h, etc.

[0116] In some embodiments, the method for preparing the high-nickel cobalt-free precursor includes the following steps:

[0117] Prepare a mixed salt solution of nickel and manganese salts;

[0118] A mixture of ammonia solution and NaOH solution was prepared, and water was added to adjust the pH to 11-12 to form a base solution.

[0119] A mixed salt solution of nickel and manganese salts was added to the substrate to carry out a second coprecipitation reaction, thereby preparing a high-nickel cobalt-free precursor with the target particle size.

[0120] In some embodiments, the conditions for the second coprecipitation reaction satisfy one or more of the following characteristics:

[0121] (1) The concentration of ammonia solution is 4 mol / L to 10 mol / L (such as 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, etc.);

[0122] (2) The concentration of NaOH aqueous solution is 4 mol / L to 10 mol / L (such as 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, etc.);

[0123] (3) The pH of the system is 11~12 (such as 11, 11.2, 11.4, 11.6, 11.8, 12, etc.).

[0124] (4) The reaction temperature is 50℃~60℃ (e.g., 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, etc.).

[0125] (5) During the second coprecipitation reaction, the ammonia concentration in the system is 4 g / L to 10 g / L, for example, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, etc.

[0126] (6) The second coprecipitation reaction is carried out under stirring at a speed of 500 r / min to 600 r / min, such as 500 r / min, 520 r / min, 540 r / min, 560 r / min, 580 r / min, 600 r / min, etc.

[0127] In some embodiments, the concentration of nickel salt in the mixed salt solution is 1 mol / L to 2 mol / L, such as 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, etc.

[0128] In some embodiments, the concentration of manganese salt in the mixed salt solution is 0.05 mol / L to 0.5 mol / L, such as 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0129] In some embodiments, the nickel salt includes at least one of nickel sulfate, nickel nitrate, and nickel chloride.

[0130] In some embodiments, the manganese salt includes at least one of manganese sulfate, manganese nitrate, and manganese chloride.

[0131] In some embodiments, the primary particles of the high-nickel cobalt-free precursor are stacked in a nanosheet-like manner.

[0132] Thirdly, this application provides a high-entropy, high-nickel, cobalt-free precursor prepared by the preparation method described in the second aspect.

[0133] Fourthly, this application provides a method for preparing a high-entropy, high-nickel, cobalt-free single-crystal cathode material, comprising the following steps:

[0134] The high-entropy, high-nickel, cobalt-free precursor described in the first or third aspect is mixed with a lithium salt and calcined in an oxygen-containing atmosphere to prepare the high-entropy, high-nickel, cobalt-free single-crystal cathode material.

[0135] In some embodiments, the molar ratio of lithium in the lithium salt to transition metal in the high-entropy, high-nickel, cobalt-free precursor is (1-1.1):1, for example, 1:1, 1.02:1, 1.04:1, 1.06:1, 1.08:1, 1.1:1, etc.

[0136] In some embodiments, the lithium salt includes at least one of lithium carbonate and lithium hydroxide.

[0137] In some embodiments, the calcination conditions include: sequentially performing a first calcination and a second calcination, wherein the temperature of the first calcination is 400℃~600℃, such as 400℃, 450℃, 500℃, 550℃, 600℃, etc.; and the temperature of the second calcination is 795℃~895℃, such as 795℃, 800℃, 810℃, 820℃, 840℃, 860℃, 880℃, 890℃, 895℃, etc.

[0138] Optionally, the first calcination time is 2h to 8h, for example, 2h, 4h, 6h, 8h, etc.;

[0139] Optionally, the second calcination time is 10h to 20h, such as 10h, 12h, 14h, 16h, 18h, 20h, etc.

[0140] Fifthly, this application provides a high-entropy, high-nickel, cobalt-free single-crystal cathode material prepared by the preparation method of the high-entropy, high-nickel, cobalt-free single-crystal cathode material described in the fourth aspect;

[0141] Optionally, the high-entropy, high-nickel, cobalt-free single-crystal cathode material includes a core and a coating layer covering at least a portion of the surface of the core; the core includes lithium nickel manganese oxide; the coating layer includes high-entropy doped lithium nickel manganese oxide; the doping elements in the high-entropy doped lithium nickel manganese oxide include titanium, magnesium, aluminum, zirconium, and molybdenum;

[0142] Optionally, the molecular formula of the lithium nickel manganese oxide is LiNi. a Mn 1-a(OH)2; where a≥0.9, optionally a is 0.9~0.96;

[0143] Optionally, the high-entropy doped lithium nickel manganese oxide has the molecular formula LiNi. b Mn 1-b-c1-c2-c3-c4- c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, c1, c2, c3, c4 and c5 are each independently 0.001~0.02; further optionally, a is 0.9~0.96.

[0144] The high-entropy, high-nickel, cobalt-free single-crystal cathode material provided in this application, by coating the surface of the core layer containing the first nickel-manganese hydroxide with a high-entropy doped shell containing titanium, magnesium, aluminum, zirconium and molybdenum, is beneficial to reduce the exposure of the {010} active crystal plane in the precursor, promote the preferential growth of the cathode material along the (003) plane, and thus improve the electrochemical performance and cycle stability of the high-entropy, high-nickel, cobalt-free single-crystal cathode material.

[0145] Furthermore, the lithium nickel manganese oxide core provides high specific capacity, while the high-entropy-doped lithium nickel manganese oxide coating can optimize the synergistic effect among multiple elements through the "entropy stabilization" effect. On the one hand, the uniform doping of high-entropy multiple elements forms a stable solid solution, effectively dispersing stress and reducing material volume changes, thereby alleviating the lifespan decay caused by material expansion and contraction during charging and discharging. On the other hand, this doping strategy effectively reduces the exposure of the {010} active crystal plane of the precursor, thereby suppressing the initial lithiation reaction rate and reducing the amount of lithium intercalation per unit time. This is beneficial for the cathode material to preferentially grow and fuse along the (003) plane during sintering, forming larger and better dispersed single crystal particles, while maintaining the chemical short-range disorder structure unique to the high-entropy state, creating more low-energy-barrier lithium-ion diffusion channels, enhancing Li⁺ diffusion kinetics, and ultimately improving the electrochemical performance and cycle stability of the material. Furthermore, the mechanism by which low {010} exposure of the precursor promotes the preferential growth of the (003) facet of the cathode material can be attributed to the following core factors and synergistic effects: the reduction of active crystal faces fundamentally reduces the lithium insertion rate, making the lithiation process mild and controllable; the residual molten salt effectively fills the interparticle gaps, improving the solid-solid interface contact; in addition, the electron delocalization effect of oxygen coordination reduces the ion migration barrier on the (003) surface, further accelerating grain fusion and orientation growth.

[0146] Sixthly, this application provides a lithium-ion battery, including a positive electrode sheet, wherein the positive electrode sheet includes a positive active material layer;

[0147] The positive electrode active material layer includes the high-nickel cobalt-free single-crystal positive electrode material described in the fifth aspect.

[0148] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this application document first, or refer to experimental manuals or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer.

[0149] Example 1

[0150] 1) Synthesis of the first nickel-manganese hydroxide in the core layer: Mixed salt solutions of nickel sulfate and manganese sulfate with concentrations of 1.54 mol / L and 0.17 mol / L, respectively, were prepared according to stoichiometric ratios. A 10 mol / L ammonia solution (ammonia acting as a precipitant and complexing agent with metal ions) and a 10 mol / L NaOH solution were added to the reactor as the base solution (the volume ratio of ammonia solution to NaOH solution was 1:1), and an appropriate amount of water was added to adjust the pH of the base solution to 11-12. Subsequently, the mixed salt solution of nickel sulfate and manganese sulfate was slowly added to carry out a co-precipitation reaction, while controlling the ammonia concentration in the reaction system to 8 g / L and adjusting the pH of the system to 11-12. The reaction was carried out at 600 r / min and 55℃ until the target particle size (D50 of 1.5 μm) was reached, thus preparing the first nickel-manganese hydroxide Ni with a D50 of 1.5 μm. 0.9 Mn 0.1 The reaction solution of (OH)2, with the first nickel-manganese hydroxide denoted as NM9010-1.5μm, shows that its primary particles are stacked in a nanosheet-like manner, as shown in the SEM image. Figure 2 .

[0151] 2) Synthesis of high-entropy, high-nickel, cobalt-free precursors: Titanium oxysulfate, magnesium sulfate heptahydrate, aluminum sulfate octadecyl hydrate, zirconium sulfate tetrahydrate, and ammonium molybdate tetrahydrate were added to a mixed solution of nickel sulfate and manganese sulfate to prepare a first mixture with a metal ion concentration of 100 g / L. The molar percentages of the transition metal elements in the first mixture were 1 mol%, 1 mol%, 1 mol%, 1 mol%, 1 mol%, 5 mol%, and 90 mol%, respectively.

[0152] The first mixture was slowly added at a rate of 0.6 L / h to the first nickel-manganese hydroxide Ni containing a D50 of 1.5 μm from step 1). 0.9 Mn 0.1In the (OH)₂ reaction solution, the reaction conditions were adjusted to an ammonia concentration of 8 g / L and a pH of 10.5–11. The reaction was carried out at 600 r / min and 55 °C until the target shell thickness (0.5 μm) was reached, forming a high-entropy doped shell (0.5 μm thick) on the surface of the first nickel-manganese hydroxide, yielding the high-entropy, high-nickel, cobalt-free precursor NM9010-HE (core-shell). Its SEM image is shown below. Figure 3 .

[0153] 3) High-nickel cobalt-free single-crystal cathode material: The high-entropy high-nickel cobalt-free precursor NM9010-HE (core-shell) from step 2) was mixed with lithium hydroxide. The molar ratio of lithium in the lithium salt to the transition metal element in the high-entropy high-nickel cobalt-free precursor, n(Li) / n(TM), was 1.04:1. The uniformly mixed sample was placed in a tube furnace and sintered under an oxygen atmosphere. The sintering process consisted of calcination at 500℃ for 6 hours and calcination at 845℃ for 16 hours, followed by natural cooling to room temperature. The sintered sample was then crushed and sieved to obtain the high-entropy high-nickel cobalt-free single-crystal cathode material LNM9010-HE (core-shell).

[0154] 4) Assembly of coin cells: The high-entropy, high-nickel, cobalt-free single-crystal cathode material LNM9010-HE (core-shell) from step 3) is used as the cathode material. It is mixed with a conductive agent (conductive carbon black SP) and a binder (PVDF) at a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) is added and stirred thoroughly to obtain a cathode slurry with a solid content of 65wt%. This slurry is then coated onto a current collector (aluminum foil, areal density of 7.5 mg / cm³). 2 The positive electrode is made by forming a positive electrode sheet. The positive electrode sheet, liquid electrolyte (1M LiPF6, solvent is DMC:EC:EMC with a volume ratio of 1:1:1), lithium negative electrode, polypropylene separator (25μm), spring sheet, positive electrode shell and negative electrode shell are assembled into a lithium-ion coin cell.

[0155] Example 2

[0156] Except for the core layer, the first nickel-manganese hydroxide is a Ni with a D50 of 2.5 μm. 0.9 Mn 0.1 Except for (OH)2, the rest is the same as in Example 1, and the specific conditions for step 1 are as follows:

[0157] Prepare a mixed salt solution of nickel sulfate and manganese sulfate with concentrations of 1.54 mol / L and 0.17 mol / L, respectively, according to stoichiometric ratios. Add a 10 mol / L ammonia solution (ammonia acts as a precipitant and complexing agent with metal ions) and a 10 mol / L NaOH solution as the base solution (the volume ratio of ammonia solution to NaOH solution is 1:1), and add an appropriate amount of water to adjust the pH of the base solution to 11-12. Then, slowly add the mixed salt solution of nickel sulfate and manganese sulfate to carry out a co-precipitation reaction, while controlling the ammonia concentration in the reaction system to 8 g / L and adjusting the pH of the system to 11-12. React at 550 r / min and 55℃ until the target particle size (D50 of 2.5 μm) is reached, thus preparing the first nickel-manganese hydroxide Ni with a D50 of 2.5 μm. 0.9 Mn 0.1 The reaction solution of (OH)2, with the first nickel-manganese hydroxide denoted as NM9010-2.5μm, shows that its primary particles are stacked in a nanosheet-like manner, as shown in the SEM image. Figure 4 .

[0158] Example 3

[0159] 1) Synthesis of the first nickel-manganese hydroxide in the core layer: Mixed salt solutions of nickel sulfate and manganese sulfate with concentrations of 1.64 mol / L and 0.07 mol / L, respectively, were prepared according to stoichiometric ratios. A 10 mol / L ammonia solution (ammonia acting as a precipitant and complexing agent with metal ions) and a 10 mol / L NaOH solution were added to the reactor as the base solution (the volume ratio of ammonia solution to NaOH solution was 1:1), and an appropriate amount of water was added to adjust the pH of the base solution to 11-12. Subsequently, the mixed salt solution of nickel sulfate and manganese sulfate was slowly added to carry out a co-precipitation reaction, while controlling the ammonia concentration in the reaction system to 8 g / L and adjusting the pH of the system to 11-12. The reaction was carried out at 550 r / min and 55℃ until the target particle size (D50 of 1.5 μm) was reached, thus preparing the first nickel-manganese hydroxide Ni with a D50 of 1.5 μm. 0.96 Mn 0.04 The reaction solution of (OH)2 (which is stacked in nanosheet form).

[0160] 2) Synthesis of high-entropy, high-nickel, cobalt-free precursor: Titanium oxysulfate, magnesium sulfate heptahydrate, aluminum sulfate octahydrate, zirconium sulfate tetrahydrate, and ammonium molybdate tetrahydrate were added to a mixed solution of nickel sulfate and manganese sulfate to prepare a first mixture with a concentration of 100 g / L. The molar percentages of the transition metal elements in the first mixture were 0.1 mol%, 0.1 mol%, 0.1 mol%, 0.1 mol%, 0.1 mol%, 3.5 mol%, and 96 mol%, respectively.

[0161] The first mixture was slowly added at a rate of 0.8 L / h to the first nickel-manganese hydroxide Ni containing a D50 of 1.5 μm from step 1). 0.9 Mn 0.1 In the reaction solution of (OH)2, the reaction conditions were adjusted to an ammonia concentration of 7 g / L and a pH of 10.5-11. The reaction was carried out at a rotation speed of 600 r / min and a temperature of 50°C until the target shell thickness (1 μm) was reached, forming a high-entropy doped shell (1 μm thick) on the surface of the first nickel manganese hydroxide, thus obtaining a high-entropy, high-nickel, cobalt-free precursor.

[0162] 3) High-nickel cobalt-free single-crystal cathode material: The high-entropy high-nickel cobalt-free precursor from step 2) is mixed with lithium hydroxide, with a molar ratio of lithium element in the lithium salt to transition metal element in the high-entropy high-nickel cobalt-free precursor, n(Li) / n(TM), of 1:1. The uniformly mixed sample is placed in a tube furnace and sintered under an oxygen atmosphere. The sintering process involves calcination at 400℃ for 8 hours, followed by calcination at 895℃ for 10 hours, and then natural cooling to room temperature. The sintered sample is then crushed and sieved to obtain the high-entropy high-nickel cobalt-free single-crystal cathode material.

[0163] 4) Assembly of button cells: Same as in Example 1.

[0164] Example 4

[0165] 1) Synthesis of the first nickel-manganese hydroxide in the core layer: Mixed salt solutions of nickel sulfate and manganese sulfate with concentrations of 1.54 mol / L and 0.17 mol / L, respectively, were prepared according to stoichiometric ratios. A 10 mol / L ammonia solution (ammonia acting as a precipitant and complexing agent with metal ions) and a 10 mol / L NaOH solution were added to the reactor as the base solution (the volume ratio of ammonia solution to NaOH solution was 1:1), and an appropriate amount of water was added to adjust the pH of the base solution to 11-12. Subsequently, the mixed salt solution of nickel sulfate and manganese sulfate was slowly added to carry out a co-precipitation reaction, while controlling the ammonia concentration in the reaction system to 8 g / L and adjusting the pH of the system to 11-12. The reaction was carried out at 500 r / min and 55℃ until the target particle size (D50 of 3 μm) was reached, thus preparing the first nickel-manganese hydroxide Ni with a D50 of 3 μm. 0.9 Mn 0.1 The reaction solution of (OH)2 (which is stacked in nanosheet form).

[0166] 2) Synthesis of high-entropy, high-nickel, cobalt-free precursor: Titanium sulfate, magnesium sulfate heptahydrate, aluminum sulfate octahydrate, zirconium sulfate tetrahydrate, and ammonium molybdate tetrahydrate were added to a mixed solution of nickel sulfate and manganese sulfate to prepare a first mixture with a concentration of 100 g / L. The molar percentages of the transition metal elements in the first mixture were 2 mol%, 2 mol%, 2 mol%, 2 mol%, 1 mol%, 1 mol%, and 90 mol%, respectively.

[0167] The first mixture was slowly added at a rate of 0.4 L / h to the first nickel-manganese hydroxide Ni containing a D50 of 3 μm from step 1). 0.9 Mn 0.1 In the reaction solution of (OH)2, the reaction conditions were adjusted to an ammonia concentration of 10 g / L and a pH of 10.5-11. The reaction was carried out at a rotation speed of 650 r / min and a temperature of 60 °C until the target shell thickness (0.25 μm) was reached, forming a high-entropy doped shell (0.25 μm) on the surface of the first nickel manganese hydroxide, thus obtaining a high-entropy, high-nickel, cobalt-free precursor.

[0168] 3) High-nickel cobalt-free single-crystal cathode material: The high-entropy high-nickel cobalt-free precursor from step 2) is mixed with lithium hydroxide, and the molar ratio of lithium element in the lithium salt to transition metal element in the high-entropy high-nickel cobalt-free precursor, n(Li) / n(TM), is 1.1:1. The uniformly mixed sample is placed in a tube furnace and sintered under an oxygen atmosphere. The sintering process is calcination at 600℃ for 2 hours, calcination at 795℃ for 20 hours, followed by natural cooling to room temperature. The sintered sample is then crushed and sieved to obtain the high-entropy high-nickel cobalt-free single-crystal cathode material.

[0169] 4) Assembly of button cells: Same as in Example 1.

[0170] Comparative Example 1

[0171] Except for the absence of a high-entropy doped shell (i.e., step 2 is omitted), the process is the same as in Example 1, and the single-crystal cathode material prepared is denoted as LNM9010-1.5μm.

[0172] Comparative Example 2

[0173] Except for the absence of a high-entropy doped shell (i.e., step 2 is omitted), the process is the same as in Example 2. The single-crystal cathode material prepared is denoted as LNM9010-2.5μm.

[0174] Comparative Example 3

[0175] Except for the high-entropy doped shell, which uses only Ti, Al, and Mo as doping elements, the rest is the same as in Example 1. The specific process is as follows:

[0176] 1) Synthesis of the first nickel-manganese hydroxide in the core layer: Same as in Example 1.

[0177] 2) Synthesis of high-entropy, high-nickel, cobalt-free precursor: Titanium oxysulfate, aluminum sulfate octadecade, and ammonium molybdate tetrahydrate were added to a mixed solution of nickel sulfate and manganese sulfate to prepare a first mixture with a concentration of 100 g / L. The molar percentages of Ti, Al, Mo, Mn, and Ni in the first mixture were 1 mol%, 1 mol%, 1 mol%, 7 mol%, and 90 mol%, respectively.

[0178] The first mixture was slowly added at a rate of 0.6 L / h to the first nickel-manganese hydroxide Ni containing a D50 of 1.5 μm from step 1). 0.9 Mn 0.1 In the reaction solution of (OH)2, the reaction conditions were adjusted to an ammonia concentration of 8 g / L and a pH of 10.5-11. The reaction was carried out at a rotation speed of 600 r / min and a temperature of 55°C until the target shell thickness (0.5 μm) was reached, forming a high-entropy doped shell (0.5 μm) on the surface of the first nickel manganese hydroxide, thus obtaining a high-entropy, high-nickel, cobalt-free precursor.

[0179] 3) High-nickel cobalt-free single-crystal cathode material: Same as Example 1.

[0180] 4) Assembly of button cells: Same as in Example 1.

[0181] Comparative Example 4

[0182] Except for replacing Mg with an equimolar amount of Zr in the high-entropy doped shell (and replacing magnesium sulfate heptahydrate with zirconium sulfate tetrahydrate to keep the molar amounts of magnesium and zirconium consistent), the rest is the same as in Example 1.

[0183] Comparative Example 5

[0184] Except for replacing Zr with an equimolar amount of Mg in the high-entropy doped shell (replacing zirconium sulfate tetrahydrate with magnesium sulfate heptahydrate to maintain the same molar amounts of zirconium and magnesium), the rest is the same as in Example 1.

[0185] Test case

[0186] 1. XRD Testing: XRD tests were performed on the first nickel-manganese hydroxide NM9010-1.5μm and NM9010-2.5μm, the high-entropy high-nickel cobalt-free precursor NM9010-HE (core-shell) of Example 1, and the cathode materials of Examples 1 and Comparative Examples 1-2. The results are shown in [Figure 1]. Figures 5-8The intensity ratios of the (100) and (001) XRD diffraction peaks of NM9010-HE (core-shell), NM9010-1.5μm, and NM9010-2.5μm are 0.47, 0.92, and 0.67, respectively. It can be seen that the precursor with the high-entropy doped layer in Example 1 has a lower degree of exposure of the {010} active crystal plane compared with NM9010-1.5μm. That is, the formation of the high-entropy doped layer is beneficial to reducing the degree of exposure of the {010} active crystal plane.

[0187] Combination Figure 8 It can be seen that the low exposure of the {010} active crystal face of the precursor can suppress the initial lithiation reaction rate and reduce the amount of lithium intercalation per unit time, which is beneficial to the preferential growth and fusion of the cathode material along the (003) face during sintering, forming single crystal particles with larger size and better dispersion. Moreover, the intensity ratios of the (003) / (104) XRD diffraction peaks of LNM9010-HE (core-shell), LNM9010-1.5μm, and LNM9010-2.5μm are 1.72, 1.67, and 1.61, respectively. It can be seen that the single crystal cathode material with high entropy doping layer in Example 1 has a lower degree of lithium-nickel mixing, which ultimately effectively improves the electrochemical performance and cycle stability of the cathode material.

[0188] 2. The performance of the lithium-ion coin cells in the examples and comparative examples was tested using the Blue Electric testing system:

[0189] At 25°C, the battery was charged to 4.25V at a rate of 0.1C (1C = 185mAh / g), and then discharged to 2.5V at a rate of 0.1C. This constitutes one cycle. The discharge capacity of this cycle is the first-cycle discharge specific capacity, and the ratio of the first-cycle charge specific capacity to the first-cycle discharge specific capacity is the first-cycle efficiency. Subsequently, 50 cycles of 1C charge-discharge were performed (2.5~4.25V). The 50-cycle capacity retention rate was calculated using the ratio of the discharge capacity of the 50th cycle to the discharge capacity of the first cycle. The 0.1C first-cycle charge-discharge curves of the batteries in Example 1 and Comparative Examples 1-2 are shown below. Figure 9 The 1C cycle stability test results of the batteries in Example 1 and Comparative Examples 1-2 are shown in [reference needed]. Figure 10 It can be seen that the battery of Example 1 has better charge / discharge specific capacitance, first efficiency, and cycle stability compared to the batteries of Comparative Examples 1-2.

[0190] Table 1. Reactor structure and process parameters of the examples and comparative examples

[0191]

[0192] As can be seen from Table 1, the high-entropy, high-nickel, cobalt-free precursors provided in Examples 1-4 of this application, by coating the surface of the core layer containing the first nickel manganese hydroxide with a high-entropy doped shell layer containing titanium, magnesium, aluminum, zirconium, and molybdenum, are beneficial to reduce the intensity ratio of the (100) and (001) of the precursor, that is, to reduce the exposure degree of the {010} active crystal plane in the precursor, promote the preferential growth of the cathode material along the (003) plane, thereby improving the electrochemical performance and cycle stability of the high-entropy, high-nickel, cobalt-free single crystal cathode material, and improving the first efficiency and capacity retention rate of the battery.

[0193] Comparing Example 1 and Comparative Example 1, and Comparative Example 2 and Comparative Example 2, it can be seen that the setting of the high-entropy doped shell in this application is beneficial to reducing the intensity ratio of the precursor (100) and (001), that is, reducing the exposure degree of the {010} active crystal plane in the precursor, promoting the preferential growth of the cathode material along the (003) plane, thereby improving the electrochemical performance and cycle stability of the high-entropy high-nickel cobalt-free single crystal cathode material, and correspondingly improving the first efficiency and capacity retention of the battery.

[0194] Comparing Example 1 and Comparative Example 3, it can be seen that by introducing Mg and Zr into the high-entropy doped shell, this application can achieve an "entropy stabilization" effect, which is beneficial to reduce the exposure of the {010} active crystal plane in the precursor, improve the electrochemical performance and cycle stability of the high-entropy high-nickel cobalt-free single crystal cathode material, and correspondingly improve the first efficiency and capacity retention of the battery.

[0195] Comparing Example 1 and Comparative Examples 4-5, it can be seen that by simultaneously introducing Mg and Zr into the high-entropy doped shell, this application can achieve synergistic enhancement, further reducing the exposure of the {010} active crystal plane in the precursor, improving the electrochemical performance and cycle stability of the high-entropy, high-nickel, cobalt-free single-crystal cathode material, and correspondingly improving the first-efficiency and capacity retention of the battery.

[0196] 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.

[0197] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection 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 scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of this application.

Claims

1. A high-entropy, high-nickel, cobalt-free precursor, characterized in that, It includes a core layer and a high-entropy doped shell layer covering at least a portion of the surface of the core layer; The core layer comprises a first nickel-manganese hydroxide; The high-entropy doped shell includes a high-entropy doped second nickel-manganese hydroxide; the doping elements in the high-entropy doped second nickel-manganese hydroxide include titanium, magnesium, aluminum, zirconium and molybdenum.

2. The high-entropy, high-nickel, cobalt-free precursor as described in claim 1, characterized in that, The high-entropy, high-nickel, cobalt-free precursor satisfies one or more of the following characteristics: (1) Based on a molar amount of nickel and manganese of 100 mol%, the nickel content in the first nickel-manganese hydroxide and the second nickel-manganese hydroxide is independently greater than or equal to 90 mol%, which can be selected as 90 mol% to 96 mol%; (2) The molecular formula of the first nickel-manganese hydroxide is Ni a Mn 1-a (OH)2; where a≥0.9, optionally a is 0.9~0.96; (3) The D50 of the core layer is 1.5 μm to 3 μm; (4) Based on a molar amount of transition metal elements of 100 mol%, the doping amounts of titanium, magnesium, aluminum, zirconium and molybdenum in the high-entropy doped second nickel-manganese hydroxide are each 0.1 mol% to 2 mol%; (5) The molecular formula of the high-entropy doped second nickel-manganese hydroxide is Ni b Mn 1-b-c1-c2-c3-c4- c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, c1, c2, c3, c4 and c5 are each independently 0.001~0.02; further optionally, a is 0.9~0.96; (6) The thickness of the high-entropy doped shell is 0.25 μm to 1 μm.

3. A method for preparing a high-entropy, high-nickel, cobalt-free precursor, characterized in that, Includes the following steps: Provide a first nickel-manganese hydroxide to form a reaction solution containing the first nickel-manganese hydroxide; Titanium salt, magnesium salt, aluminum salt, zirconium salt, molybdenum salt, nickel salt and manganese salt are first mixed to form a first mixture; The first mixture is added to the reaction solution containing the first nickel-manganese hydroxide, and a first coprecipitation reaction is carried out to form a high-entropy doped shell of the target thickness on the surface of the first nickel-manganese hydroxide, thereby preparing the high-entropy, high-nickel, cobalt-free precursor.

4. The method for preparing the high-entropy, high-nickel, cobalt-free precursor as described in claim 3, characterized in that, The preparation method satisfies one or more of the following characteristics: (1) The titanium salt includes at least one of titanium oxysulfate and titanium sulfate; (2) The magnesium salt includes magnesium sulfate; (3) The aluminum salts include aluminum sulfate; (4) The zircon salt includes zirconium sulfate; (5) The molybdenum salt includes ammonium molybdate; (6) The nickel salt includes nickel sulfate; (7) The manganese salt includes manganese sulfate; (8) With the molar amounts of nickel and manganese being 100 mol%, the nickel content in the first nickel-manganese hydroxide and the high-entropy doped shell is independently greater than or equal to 90 mol%, which can be selected as 90 mol% to 96 mol%. (9) Based on a total molar amount of manganese and nickel of 100 mol%, the content of titanium, magnesium, aluminum, zirconium and molybdenum in the first mixture is 0.1 mol% to 2 mol%. (10) The molecular formula of the first nickel-manganese hydroxide is Ni a Mn 1-a (OH)2; where a≥0.9, optionally a is 0.9~0.96; (11) The D50 of the first nickel-manganese hydroxide is 1.5 μm to 3 μm; (12) The target thickness is 0.25 μm to 1 μm; (13) The high-entropy doped shell includes a high-entropy doped second nickel-manganese hydroxide with the molecular formula Ni b Mn 1-b-c1-c2-c3-c4-c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, c1, c2, c3, c4 and c5 are each independently 0.001~0.02; further optionally, a is 0.9~0.

96.

5. The method for preparing the high-entropy, high-nickel, cobalt-free precursor as described in claim 3 or 4, characterized in that, The conditions for the first coprecipitation reaction must satisfy one or more of the following characteristics: (1) The ammonia concentration is 7 g / L to 10 g / L; (2) pH is 10.5~11; (3) The stirring speed is 550 r / min to 650 r / min; (4) The reaction temperature is 50℃~60℃.

6. The high-entropy high-nickel cobalt-free precursor prepared by the method for preparing the high-entropy high-nickel cobalt-free precursor according to any one of claims 3 to 5.

7. A method for preparing a high-entropy, high-nickel, cobalt-free single-crystal cathode material, characterized in that, Includes the following steps: The high-entropy, high-nickel, cobalt-free precursor of claim 6 is mixed with lithium salt and calcined in an oxygen-containing atmosphere to prepare the high-entropy, high-nickel, cobalt-free single-crystal cathode material.

8. The method for preparing the high-entropy, high-nickel, cobalt-free single-crystal cathode material as described in claim 7, characterized in that, The preparation method satisfies one or more of the following characteristics: (1) The molar ratio of lithium in the lithium salt to transition metal in the high-entropy, high-nickel, cobalt-free precursor is (1-1.1):1; (2) The lithium salt includes at least one of lithium carbonate and lithium hydroxide; (3) The calcination conditions include: performing the first calcination and the second calcination in sequence, with the temperature of the first calcination being 400℃~600℃ and the temperature of the second calcination being 795℃~895℃; Optionally, the first calcination time is 2 hours to 8 hours; Optionally, the second calcination time is 10h to 20h.

9. The high-entropy, high-nickel, cobalt-free single-crystal cathode material prepared by the preparation method of the high-entropy, high-nickel, cobalt-free single-crystal cathode material as described in claim 7 or 8; Optionally, the high-entropy, high-nickel, cobalt-free single-crystal cathode material includes a core and a coating layer covering at least a portion of the surface of the core; the core includes lithium nickel manganese oxide; the coating layer includes high-entropy doped lithium nickel manganese oxide; the doping elements in the high-entropy doped lithium nickel manganese oxide include titanium, magnesium, aluminum, zirconium, and molybdenum; Optionally, the molecular formula of the lithium nickel manganese oxide is LiNi. a Mn 1-a (OH)2; where, a ≥ 0.9, or optionally, a is 0.9 to 0.96; Optionally, the high-entropy doped lithium nickel manganese oxide has the molecular formula LiNi. b Mn 1-b-c1-c2-c3-c4- c5 Ti c1 Mg c2 Al c2 Zr c4 Mo c5 (OH)2; wherein b≥0.9, c1, c2, c3, c4 and c5 are each independently 0.001~0.02; further optionally, a is 0.9~0.

96.

10. A lithium-ion battery, characterized in that, Includes a positive electrode sheet, wherein the positive electrode sheet includes a positive active material layer; The positive electrode active material layer includes the high-nickel cobalt-free single-crystal positive electrode material as described in claim 9.

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