Manganese-doped lithium nickel oxide positive electrode material, preparation method thereof, positive electrode sheet, battery and electric device

Abstract

The application relates to a manganese-doped lithium nickelate positive electrode material and a preparation method thereof, a positive electrode sheet, a battery and an electric device, the preparation method comprising the following steps: S1, mixing a nickel-manganese hydroxide precursor, a first lithium source and a chloride, and then obtaining an intermediate product through a molten salt method under an oxygen atmosphere, wherein the intermediate product comprises single-crystal manganese-doped lithium nickelate with a manganese valence of +3; S2, mixing the intermediate product with a second lithium source, and then performing heat treatment under an oxygen atmosphere to obtain single-crystal manganese-doped lithium nickelate with a manganese valence of +4; wherein the amount of the first lithium source is 100%-130% of the molar amount of the nickel-manganese hydroxide precursor; the amount of the second lithium source is less than 15% of the mass of the intermediate product; and the holding temperature of the heat treatment is 600 DEG C-700 DEG C. The preparation method can improve the oxidation state of manganese elements, and further improves the cycle stability of the prepared positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a manganese-doped lithium nickel oxide cathode material, its preparation method, cathode sheet, battery, and electrical device. Background Technology

[0002] Rechargeable batteries such as lithium-ion batteries (LIBs) are crucial for the widespread use of portable electronic devices and electric vehicles. Cobalt-free layered lithium nickel oxide (LiNiO2), as a cathode material, boasts a high efficiency of up to 240 mAh g⁻¹. -1 The high discharge specific capacity and high operating voltage of lithium nickel oxide (LiNiO) result in higher energy density. However, conventional sintering methods produce lithium-poor phases with high mixing, which reduces their cycle performance. Furthermore, the low energy required to form oxygen vacancies in LiNiO materials leads to irreversible structural phase transitions during cycling, releasing oxygen and reducing the material's cycle stability. To improve the performance of LiNiO cathode materials, several techniques have been employed, including interface modification, particle engineering, and elemental doping.

[0003] To enhance the structural stability of materials, single-crystal modification is considered an innovative method. For example, one technique involves preparing single-crystal high-nickel ternary cathode materials via a molten salt method. This method employs high-temperature calcination of mixed molten salts to obtain single-crystal high-nickel ternary cathode materials with good crystallinity, high charge-discharge capacity, and low discharge capacity decay rate. However, although this single-crystal modification can partially solve the problem of irreversible structural phase transitions, other improvement methods are still needed to further enhance cycle performance.

[0004] Incorporating manganese is considered a method to improve the cycle stability of lithium nickel oxide. For example, by using cobalt-free layered nickel-manganese cathode materials, the crystal structure of lithium nickel oxide cathode materials can be stabilized, thereby improving the material's stability. However, the synthesis process of single-crystal nickel-manganese cathode materials generally requires water washing to remove molten salt. This water washing process can induce Li... + / H + The oxidation state of manganese decreases (from +4 to +3). +3 manganese induces the Jameer-Taylor effect, leading to structural distortion. Furthermore, compared to +4 manganese, +3 manganese possesses more single electrons in its 3d orbitals and exhibits a stronger magnetoresistance effect, further contributing to the structural instability of lithium nickelate materials. Therefore, effective strategies are needed to improve the oxidation state of manganese and synthesize high-performance single-crystal manganese-doped lithium nickelate cathode materials. Summary of the Invention

[0005] Therefore, it is necessary to provide a manganese-doped lithium nickelate cathode material and its preparation method, which can improve the oxidation state of manganese and thus enhance the cycle stability of the prepared cathode material.

[0006] In addition, this application also provides a positive electrode, a battery, and an electrical device.

[0007] This application provides a method for preparing a manganese-doped lithium nickelate cathode material, comprising the following steps:

[0008] S1. After mixing the nickel manganese hydroxide precursor, the first lithium source and the chloride, an intermediate product is obtained by molten salt reaction under an oxygen atmosphere. The intermediate product contains single-crystal manganese-doped lithium nickelate with a manganese valence state of +3.

[0009] S2. The intermediate product is mixed with a second lithium source and then heat-treated in an oxygen atmosphere to obtain a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence state of +4.

[0010] The amount of the first lithium source is 100% to 130% of the molar amount of the nickel-manganese hydroxide precursor; the amount of the second lithium source is less than 15% of the mass of the intermediate product; and the heat treatment temperature is 600℃ to 700℃.

[0011] In some embodiments, the nickel-manganese hydroxide precursor is Ni 0.95 Mn 0.05 (OH) x The precursor, the single-crystal manganese-doped lithium nickelate cathode material with a manganese valence state of +4, has the molecular formula Li. 1+x (Ni 0.95 Mn 0.05 ) 1-x O2, -0.1 ≤ x < 0.2.

[0012] In some embodiments, the holding temperature of the molten salt method is 600℃~700℃, the holding time is 10 h~20 h, and the rate of heating to the holding temperature of the molten salt method is 1 ℃ / min~10 ℃ / min.

[0013] In some embodiments, the heat treatment holding time is 0.5 h to 6 h, and the rate of heating to the heat treatment holding temperature is 1 ℃ / min to 10 ℃ / min.

[0014] In some embodiments, the first lithium source and the second lithium source each independently comprise at least one of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate; and / or,

[0015] The mass ratio between the second lithium source and the intermediate product is 10% to 12%.

[0016] In some embodiments, the chloride includes at least one selected from sodium chloride, potassium chloride, lithium chloride, ferric chloride, calcium chloride, and copper chloride; and / or,

[0017] The molar ratio of the chloride to the nickel-manganese hydroxide precursor is <1.

[0018] This application also provides a manganese-doped lithium nickelate cathode material, which is prepared using the above-described preparation method.

[0019] This application also provides a positive electrode sheet, comprising the aforementioned manganese-doped lithium nickelate positive electrode material.

[0020] This application also provides a battery comprising the aforementioned manganese-doped lithium nickelate cathode material or the aforementioned cathode sheet.

[0021] This application also provides an electrical device, including the aforementioned manganese-doped lithium nickelate cathode material, the aforementioned cathode sheet, or the aforementioned battery.

[0022] To address the issue of poor stability in manganese-doped lithium nickelate cathode materials prepared by traditional techniques, this application proposes a two-step preparation method. First, using nickel-manganese hydroxide as a precursor, a molten salt chemical method is employed, controlling the molar ratio of the first lithium source to the nickel-manganese hydroxide precursor, to obtain an intermediate product containing single-crystal manganese-doped lithium nickelate with a manganese valence of +3. Then, the intermediate product is heat-treated with a second lithium source for secondary lithiation, with the heat treatment temperature and the amount of the second lithium source controlled within a low range to regulate the stoichiometric ratio of lithium, nickel, and manganese, thereby converting the manganese valence to +4, ultimately obtaining a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +4.

[0023] The method for preparing the manganese-doped lithium nickelate cathode material described in this application eliminates the need for an additional manganese source. Instead, it uses nickel-manganese hydroxide as a precursor, adds a lithium source, and sinters, controlling the ratio of lithium to nickel and manganese to ensure sufficient oxidation of manganese to the +4 valence state. This results in a cathode material with a high specific capacity, significantly reducing modification costs. Furthermore, the manganese in the manganese-doped lithium nickelate cathode material prepared by this method is in the +4 valence state, reducing the influence of the Jan Taylor effect and superexchange effect caused by +3 manganese, and effectively improving the cycle stability of the material.

[0024] Therefore, the single-crystal manganese-doped lithium nickelate cathode material prepared by the above method has high comprehensive performance and can be applied to batteries such as lithium-ion batteries, thereby obtaining good cycle stability. Attached Figure Description

[0025] Figure 1 Ni used in Example 1 0.95 Mn 0.0 5(OH)x Scanning electron microscope image of the precursor;

[0026] Figure 2 Li is the product obtained in Example 1. 1.1 (Ni 0.95 Mn 0.05 ) 0.9 Scanning electron microscope image of O2;

[0027] Figure 3 Li is the product obtained in Example 1. 1.1 (Ni 0.95 Mn 0.05 ) 0.9 X-ray diffraction test results of O2;

[0028] Figure 4 The image shows the cycle performance curve of the button cell prepared in Example 1 at 1 C. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0030] 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this document; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, stating that a parameter is an integer ≥2 is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, stating that a parameter is an integer selected from "2-10" is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0032] This application provides a method for preparing manganese-doped lithium nickel oxide cathode material, comprising the following steps S1 to S2.

[0033] S1. After mixing the nickel manganese hydroxide precursor, the first lithium source and the chloride, the intermediate product is obtained by molten salt reaction under an oxygen atmosphere. The intermediate product contains single-crystal manganese-doped lithium nickelate with a manganese valence of +3.

[0034] S2. Mix the intermediate product with the second lithium source, and then heat-treat it in an oxygen atmosphere to obtain a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence state of +4.

[0035] The amount of the first lithium source is 100% to 130% of the molar amount of the nickel-manganese hydroxide precursor; the amount of the second lithium source is less than 15% of the mass of the intermediate product; and the heat treatment holding temperature is 600 ℃ to 700 ℃.

[0036] To address the issue of poor stability in manganese-doped lithium nickelate cathode materials prepared by traditional techniques, this application proposes a two-step preparation method. First, using nickel-manganese hydroxide as a precursor, a molten salt chemical method is employed, controlling the molar ratio of the first lithium source to the nickel-manganese hydroxide precursor, to obtain an intermediate product containing single-crystal manganese-doped lithium nickelate with a manganese valence of +3. Then, the intermediate product is heat-treated with a second lithium source for secondary lithiation, with the heat treatment temperature and the amount of the second lithium source controlled within a low range to regulate the stoichiometric ratio of lithium, nickel, and manganese, thereby converting the manganese valence to +4, ultimately obtaining a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +4.

[0037] The method for preparing the manganese-doped lithium nickelate cathode material described in this application eliminates the need for an additional manganese source. Instead, it uses nickel-manganese hydroxide as a precursor, adds a lithium source, and sinters, controlling the ratio of lithium to nickel and manganese to ensure sufficient oxidation of manganese to the +4 valence state. This results in a cathode material with a high specific capacity, significantly reducing modification costs. Furthermore, the manganese in the manganese-doped lithium nickelate cathode material prepared by this method is in the +4 valence state, reducing the influence of the Jan Taylor effect and superexchange effect caused by +3 manganese, and effectively improving the cycle stability of the material.

[0038] Therefore, the single-crystal manganese-doped lithium nickelate cathode material prepared by the above method has high comprehensive performance and can be applied to batteries such as lithium-ion batteries, thereby obtaining good cycle stability.

[0039] As an example, the amount of the first lithium source used is 100%, 110%, 120%, or 130% of the molar amount of the nickel manganese hydroxide precursor.

[0040] As an example, the mass ratio between the second lithium source and the intermediate product is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 8.5%, 9%, 9.5%, 10%, 11%, 12%, 13%, and 14%. Further, the mass ratio between the second lithium source and the intermediate product is 1% to 14%, and even further, it is 10% to 12%.

[0041] In some embodiments, the nickel manganese hydroxide precursor includes, but is not limited to, Ni 0.95 Mn 0.05 (OH) x Precursor. Further, the nickel-manganese hydroxide precursor is Ni. 0.95 Mn 0.05 (OH) x The precursor, the single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +4, has the molecular formula Li. 1+x (Ni 0.95 Mn 0.05 ) 1-xO2, -0.1 ≤ x < 0.2. Furthermore, x can be -0.1, -0.05, 0, 0.05, 0.1, or 0.15.

[0042] In some embodiments, the holding temperature of the molten salt method is 600 ℃~700 ℃, the holding time is 10 h~20 h, and the rate of heating to the holding temperature of the molten salt method is 1 ℃ / min~10 ℃ / min.

[0043] As examples, the holding temperatures for the molten salt method are 600 ℃, 630 ℃, 650 ℃, 660 ℃, 680 ℃, and 700 ℃. Further, they can be within a range defined by any two of the above values, as will be the case below. As examples, the holding times can be 10 h, 12 h, 14 h, 16 h, 18 h, and 20 h. As examples, the rates of heating to the holding temperature for the molten salt method are 1 ℃ / min, 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min, 6 ℃ / min, 8 ℃ / min, and 10 ℃ / min.

[0044] In some embodiments, the holding temperature of the heat treatment is 600 ℃~700 ℃, the holding time is 0.5h~6h, and the rate of heating to the holding temperature of the heat treatment is 1 ℃ / min~10 ℃ / min.

[0045] As examples, the holding temperatures for the heat treatment described above are 600 ℃, 630 ℃, 650 ℃, 660 ℃, 680 ℃, and 700 ℃. Further, the holding temperatures can be any two of the above values ​​used as endpoints, as will be the case below. As examples, the holding times can be 0.4 h, 12 h, 14 h, 16 h, 18 h, and 20 h. As examples, the rates of heating to the holding temperatures for the heat treatment are 1 ℃ / min, 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min, 6 ℃ / min, 8 ℃ / min, and 10 ℃ / min.

[0046] In some embodiments, both the first lithium source and the second lithium source are decomposable lithium sources; further, the first lithium source and the second lithium source each independently include at least one of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate. It is understood that the specific types of the first lithium source and the second lithium source may be the same or different.

[0047] In some embodiments, the chloride includes at least one selected from sodium chloride, potassium chloride, lithium chloride, ferric chloride, calcium chloride, and copper chloride. Further, the chloride includes at least one selected from lithium chloride and sodium chloride. Further, the molar ratio of chloride to the nickel-manganese hydroxide precursor is <1.

[0048] This application also provides a manganese-doped lithium nickelate cathode material, which is prepared using the above-described preparation method.

[0049] This application also provides a positive electrode sheet, comprising the aforementioned manganese-doped lithium nickelate positive electrode material.

[0050] In some embodiments, the positive electrode includes a current collector and an active layer. The current collector may be a metal foil. The active layer includes the aforementioned manganese-doped lithium nickelate positive electrode material. Furthermore, the active layer may also include a conductive agent and a binder.

[0051] In some embodiments, the above-mentioned positive electrode sheet can be obtained by mixing the above-mentioned manganese-doped lithium nickelate positive electrode material conductive agent, binder and solvent to form an active slurry, and then coating the active slurry onto the current collector and drying it.

[0052] In some embodiments, the mass content of the manganese-doped lithium nickelate cathode material in the active layer is 75% to 96%, for example 75%, 80%, 85%, 90%, 95%, 96%, or 98%.

[0053] In some embodiments, the mass content of the conductive agent in the active layer is 2% to 20%, for example, 2%, 5%, 8%, 10%, 15%, or 20%.

[0054] In some embodiments, the mass content of the adhesive in the active layer is 2% to 20%, for example, 2%, 5%, 8%, 10%, 15%, or 20%.

[0055] It is understood that conductive agents and binders may be reagents known in the art.

[0056] This application also provides a battery comprising the aforementioned manganese-doped lithium nickelate cathode material or the aforementioned cathode sheet.

[0057] In some embodiments, the battery further includes a negative electrode, with a positive electrode disposed opposite to the negative electrode.

[0058] The battery further includes a separator and an electrolyte, which is immersed in the positive and negative electrode plates. The electrolyte includes an electrolyte salt and a solvent. The electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0059] In some embodiments, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butene carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0060] The battery also includes a separator, which may be a separator known in the art. In some embodiments, the separator may be made of one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0061] This application also provides an electrical device, including the aforementioned manganese-doped lithium nickelate cathode material, the aforementioned cathode sheet, or the aforementioned battery.

[0062] Electrical devices can include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices can include, for example, mobile phones and laptops; electric vehicles can include, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0063] To make the objectives, technical solutions, and advantages of this invention clearer and more concise, the invention is described using the following specific embodiments, but the invention is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of the invention and can be used to describe the invention, but should not be construed as limiting the scope of the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

[0064] To better illustrate the present invention, the following embodiments are provided for further explanation. The specific embodiments are as follows.

[0065] Example 1:

[0066] A single-crystal manganese-doped lithium nickelate cathode material specifically includes the following steps:

[0067] S1. Weigh out 1.00 g of Ni. 0.95 Mn 0.05 (OH) x The precursor, 0.70 g of lithium hydroxide, 0.30 g of lithium chloride, and 0.20 g of sodium chloride were ground evenly in a mortar and placed in an alumina crucible. The crucible was then placed in a tube furnace filled with oxygen and heated to 630 °C at a rate of 5 °C / min. The temperature was maintained for 14 h and then allowed to cool naturally. The resulting material was dispersed in 100 mL of deionized water, stirred, filtered, and dried at 80 °C for 2 h to obtain a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +3.

[0068] S2. Weigh 0.50 g of the +3 manganese single-crystal manganese-doped lithium nickelate cathode material prepared in S1 and 0.05 g of lithium hydroxide. Grind them evenly in a mortar, place them in an alumina crucible, and put them in a tube furnace filled with oxygen. Heat the furnace to 680 °C at a rate of 5 °C / min, hold for 6 h, and allow to cool naturally to obtain single-crystal Li. 1.1 (Ni 0.95 Mn 0.05 ) 0.9 O2 cathode material.

[0069] A button cell, the preparation method of which includes the following steps: preparing a single crystal Li 1.1 (Ni 0.95 Mn 0.05 ) 0.9 O2 positive electrode material, super-p conductive agent, and polyvinylidene fluoride binder are mixed with N-methyl-2-pyrrolidone in a mass ratio of 8:1:1 to form a uniform slurry. The slurry is then uniformly coated onto aluminum foil using a coating method. After drying and rolling, the slurry is punched into a circular electrode sheet and vacuum dried at 120 °C for 12 h. This electrode sheet is used as the positive electrode, and a lithium metal sheet is used as the negative electrode. The electrolyte contains 1 mol / L LiPF6, and the solvent is EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio of 1:1:1). A Celgard 2500 microporous membrane is used as the separator. The slurry is then assembled into a button cell in a glove box.

[0070] Comparative Example 1:

[0071] The process is basically the same as in Example 1, except that step S2 is omitted and the single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +3 obtained in step S1 is directly used to prepare a button cell.

[0072] The preparation method of this single-crystal manganese-doped lithium nickelate cathode material includes the following steps:

[0073] S1. Weigh out 1.00 g of Ni. 0.95 Mn 0.05 (OH) x The precursor, 0.70 g of lithium hydroxide, 0.30 g of lithium chloride, and 0.20 g of sodium chloride were ground evenly in a mortar and placed in an alumina crucible. The crucible was then placed in a tube furnace filled with oxygen and heated to 630 °C at a rate of 5 °C / min. The temperature was maintained for 14 h and then allowed to cool naturally. The resulting material was dispersed in 100 mL of deionized water, stirred, filtered, and dried at 80 °C for 2 h to obtain a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +3.

[0074] A button cell battery is prepared by the following steps: A single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +3 obtained in step S1, a super-p conductive agent, and a polyvinylidene fluoride binder are mixed with N-methyl-2-pyrrolidone in a mass ratio of 8:1:1 to form a uniform slurry. This slurry is then uniformly coated onto aluminum foil using a coating method. After drying and rolling, the slurry is punched into a circular electrode sheet and vacuum-dried at 120 °C for 12 h. This electrode sheet is used as the positive electrode, a lithium metal sheet as the negative electrode, and the electrolyte contains 1 mol / L LiPF6. The solvent is EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio 1:1:1). A Celgard 2500 microporous membrane is used as the separator. The battery is then assembled into a button cell in a glove box.

[0075] Example 2:

[0076] A single-crystal manganese-doped lithium nickelate cathode material, the preparation method of which includes the following steps:

[0077] S1. Weigh out 1.00 g of Ni. 0.95 Mn 0.05 (OH) x The precursor, 1.00 g lithium nitrate, 0.30 g lithium chloride and 0.10 g sodium chloride were ground evenly in a mortar and placed in an alumina crucible. The crucible was then placed in a tube furnace filled with oxygen and heated to 630 °C at a rate of 5 °C / min. The temperature was maintained for 14 h and then allowed to cool naturally. The resulting material was dispersed in 100 mL of deionized water, stirred, filtered, and dried at 80 °C for 2 h to obtain a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +3.

[0078] S2. Weigh 0.50 g of the +3 manganese single-crystal manganese-doped lithium nickelate cathode material prepared in S1 and 0.04 g of lithium hydroxide. Grind them evenly in a mortar, place them in an alumina crucible, and put them in a tube furnace filled with oxygen. Heat the furnace to 650 °C at a rate of 5 °C / min, hold for 3 h, and allow to cool naturally to obtain single-crystal Li. 0.95 (Ni 0.95 Mn 0.05 ) 1.05 O2 cathode material.

[0079] A button cell, the preparation method of which includes the following steps: preparing a single crystal Li 0.95 (Ni 0.95 Mn 0.05 ) 1.05 O2 positive electrode material, super-p conductive agent and polyvinylidene fluoride binder are mixed with N-methyl-2-pyrrolidone in a mass ratio of 9.2:0.4:0.4 to form a uniform slurry. The slurry is then uniformly coated onto aluminum foil, dried and rolled, and punched into a circular electrode sheet. The electrode sheet is then vacuum dried at 120 °C for 12 h. Using this electrode sheet as the positive electrode and lithium metal sheet as the negative electrode, the electrolyte contains 1 mol / L LiPF6. The solvent is EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio of 1:1:1). A Celgard 2500 microporous membrane is used as the separator. The electrode sheet is assembled into a button cell in a glove box.

[0080] Example 3

[0081] The process is basically the same as in Example 1, except that in step S2, the content of lithium hydroxide is 0.06 g. Therefore, the mass ratio W of lithium hydroxide and single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +3 is different in S1. All other steps are the same.

[0082] Step S2 is as follows: Weigh 0.50 g of the +3 manganese single-crystal manganese-doped lithium nickelate cathode material prepared in S1 and 0.06 g of lithium hydroxide. Grind them evenly in a mortar, place them in an alumina crucible, and put them in a tube furnace filled with oxygen. Heat the furnace to 680 ℃ at a rate of 5 ℃ / min, hold for 6 h, and allow to cool naturally to obtain single-crystal Li. 1.1 (Ni 0.95 Mn 0.05 ) 0.9 O2 cathode material.

[0083] The following are performance tests.

[0084] The precursor used in all embodiments and comparative examples is Ni, which was used in Example 1. 0.95 Mn 0.05 (OH) xThe precursor, Ni used in Example 1 0.95 Mn 0.05 (OH) x Precursors such as Figure 1 As shown. By Figure 1 It can be seen that the precursor is a spherical secondary aggregate with a particle size of about 5 μm.

[0085] Product Li obtained in Example 1 1.1 (Ni 0.95 Mn 0.05 ) 0.9 The scanning electron microscope image and X-ray diffraction test results of O2 are as follows: Figure 2 and Figure 3 As shown. By Figure 2 and Figure 3 It can be seen that Li 1.1 (Ni 0.95 Mn 0.05 ) 0.9 The O2 cathode material consists of submicron-sized single-crystal particles.

[0086] The cycle performance curve of the button cell prepared in Example 1 at 1 C is shown below. Figure 4 As shown. The results indicate that Li 1.1 (Ni 0.95 Mn 0.05 ) 0.9 The specific discharge capacity of O2 after 80 cycles is 175 mAhg. -1 The capacity retention rate was 93%. This indicates that the product Li obtained in Example 1 has a good capacity retention rate. 1.1 (Ni 0.95 Mn 0.05 ) 0.9 O2 exhibits high cycling stability.

[0087] The discharge specific capacity and capacity retention after 80 cycles at 1 C for other embodiments and comparative examples are shown in Table 1 below. In S1, the mass ratio of lithium hydroxide to single-crystal manganese-doped lithium nickelate cathode material with a manganese valence of +3 is denoted as W.

[0088] Table 1 XPS Test Results

[0089]

[0090] As shown in Table 1, compared to the comparative example, the preparation method provided in this application, through secondary lithiation, can increase the valence state of manganese in the material. +3 valence manganese induces the Jameer-Taylor effect, leading to structural distortion. Furthermore, compared to +4 valence manganese, +3 valence manganese has more single electrons in its 3d orbitals and exhibits a stronger magnetoresistance effect, thus causing structural instability in the lithium nickelate material. Therefore, the presence of +4 valence manganese in Example 1 signifies improved stability.

[0091] 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.

[0092] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing a manganese-doped lithium nickelate cathode material, characterized in that, Includes the following steps: S1. After mixing the nickel-manganese hydroxide precursor, the first lithium source, and the chloride, an intermediate product is obtained by molten salt reaction under an oxygen atmosphere. The intermediate product contains single-crystal manganese-doped lithium nickelate with a manganese valence of +3. The holding temperature of the molten salt reaction is 600 ℃~700 ℃. S2. The intermediate product is mixed with a second lithium source and then heat-treated in an oxygen atmosphere to obtain a single-crystal manganese-doped lithium nickelate cathode material with a manganese valence state of +4. The amount of the first lithium source is 100% to 130% of the molar amount of the nickel-manganese hydroxide precursor; the mass ratio of the second lithium source to the intermediate product is 1% to 14%; and the heat treatment temperature is 600 ℃ to 700 ℃.

2. The preparation method according to claim 1, characterized in that, The nickel-manganese hydroxide precursor is Ni 0.95 Mn 0.05 (OH) x The precursor, the single-crystal manganese-doped lithium nickelate cathode material with a manganese valence state of +4, has the molecular formula Li. 1+x (Ni 0.95 Mn 0.05 ) 1-x O2, -0.1 ≤ x<0.

2.

3. The preparation method according to claim 1, characterized in that, The holding time is 10 h to 20 h, and the rate of heating to the holding temperature of the molten salt method is 1 ℃ / min to 10 ℃ / min.

4. The preparation method according to claim 1, characterized in that, The heat treatment holding time is 0.5 h to 6 h, and the rate of heating to the heat treatment holding temperature is 1 ℃ / min to 10 ℃ / min.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The first lithium source and the second lithium source each independently comprise at least one of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate; and / or, The mass ratio between the second lithium source and the intermediate product is 8% to 12%.

6. The preparation method according to any one of claims 1 to 4, characterized in that, The chloride includes at least one of sodium chloride, potassium chloride, lithium chloride, ferric chloride, calcium chloride, and copper chloride; and / or, The molar ratio of the chloride to the nickel-manganese hydroxide precursor is <1.

7. A manganese-doped lithium nickel oxide cathode material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. A positive electrode plate, characterized in that, Including the manganese-doped lithium nickelate cathode material as described in claim 7.

9. A battery, characterized in that, This includes the manganese-doped lithium nickel oxide cathode material as described in claim 7 or the cathode sheet as described in claim 8.

10. An electrical appliance, characterized in that, This includes the manganese-doped lithium nickel oxide cathode material as described in claim 7, the cathode sheet as described in claim 8, or the battery as described in claim 9.

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