Positive electrode active material, and preparation method therefor and use thereof

Abstract

A positive electrode active material, and a preparation method therefor and a use thereof. The chemical formula of the positive electrode active material is Li1+aNa xPyNi0.5+bMn1.5+cMzOd, wherein -0.1≤a≤0.2, -0.2≤b≤0.2, -0.2≤c≤0.2, 3.8≤d≤4.3, 0<x≤0.15, 0<y≤0.1, 0≤z≤0.2, and the element M is selected from at least one of Mg, Al, Ca, Sc, Ti, V, Cr, Fe, Co, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, S or F. The positive electrode active material has a high average voltage and energy density, and when the positive electrode active material is applied to a lithium ion battery, the cost can be reduced, and comprehensive cost effectiveness can be improved.

Description

Positive electrode active material and preparation method and application thereof

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 22, 2023, with application number 202311775694.1 and application name “Positive Electrode Active Materials, Preparation Methods and Applications Thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of lithium-ion batteries, and in particular to a positive electrode active material and a preparation method and application thereof. Background Art

[0003] The positive electrode active material is a key factor in determining the performance of lithium-ion batteries. Currently, positive electrode active materials include layered materials represented by LiCoO2 and ternary NCM, olivine-type materials represented by LiFePO4, and spinel-type materials represented by LiMn2O4. Among them, LiCoO2 and ternary NCM have high energy density and good cycle performance but are expensive; LiFePO4 has excellent cycle performance, good safety, and low price, but has low energy density, and its actual capacity is close to the theoretical capacity, making it difficult to significantly increase it; LiMn2O4 has a stable structure, but low capacity and serious Mn dissolution problems, poor high-temperature performance, and limited practical application scenarios.

[0004] Lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) was developed on the basis of LiMn2O4, Ni 2+ The addition of Mn 3+ Upgrade to Mn 4+ The price is significantly improved, which greatly improves the dissolution of Mn. Lithium nickel manganese oxide has a similar specific capacity to LiMn2O4 (about 146.7mAh / g), while the operating voltage of lithium nickel manganese oxide (4.75V) is about 19% higher than that of LiMn2O4 (4V), and has a higher energy density. Compared with traditional LiCoO2, NCM and LiFePO4, lithium nickel manganese oxide mainly increases energy density by increasing voltage, rather than by adding additional Li like lithium-rich layered materials. Therefore, it greatly reduces the watt-hour cost and has a very high cost-effectiveness.

[0005] However, a higher voltage makes the interface problems of lithium nickel manganese oxide particularly prominent. The oxidation of the electrolyte, interface side reactions, changes in the interface layer structure, etc. lead to poor cycling performance, high-temperature performance, and storage performance when lithium nickel manganese oxide is used as the positive electrode active material, and serious gas generation. Although phosphorus doping can effectively improve the electrochemical performance of lithium nickel manganese oxide, especially the long-term cycling stability and high-temperature performance, phosphorus doping will increase the disorder degree of lithium nickel manganese oxide, significantly increase the proportion of lithium nickel manganese oxide at the 4V charging platform, directly lead to a decrease in the average voltage of lithium nickel manganese oxide, and reduce the energy density of lithium nickel manganese oxide. To address this problem, the commonly used method at present is to perform heat preservation annealing on phosphorus-doped lithium nickel manganese oxide at a relatively low temperature (500 °C to 800 °C) for a long time (sometimes up to 30 hours), which greatly increases the preparation difficulty and cost of lithium nickel manganese oxide. Moreover, for samples with a relatively high phosphorus doping amount, even long-term annealing cannot fully eliminate the 4V platform, which greatly limits the energy density of lithium nickel manganese oxide.

[0006] Summary of the Invention

[0007] Based on this, in view of the above problems, it is necessary to provide a positive electrode active material, its preparation method and application; the positive electrode active material has a relatively high average voltage and energy density, and is beneficial to reducing costs and improving the comprehensive cost performance when used in lithium-ion batteries.

[0008] The chemical formula of a positive electrode active material is Li 1+a Na x P y Ni 0.5+b Mn 1.5+c M z O d , where -0.1 ≤ a ≤ 0.2, -0.2 ≤ b ≤ 0.2, -0.2 ≤ c ≤ 0.2, 3.8 ≤ d ≤ 4.3, 0 < x ≤ 0.15, 0 < y ≤ 0.1, 0 ≤ z ≤ 0.2, and the M element is selected from at least one of Mg, Al, Ca, Sc, Ti, V, Cr, Fe, Co, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, S or F.

[0009] In one embodiment, when the M element and the values of y and z are the same, compared with Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d , the disorder degree of the positive electrode active material is reduced by at least 15%.

[0010] In one embodiment, the full width at half maximum of the main peak of the Ni-O bond in the Raman spectrum of the positive electrode active material is 30 cm-1 to 55 cm -1 .

[0011] In one embodiment, the full width at half maximum of the main peak of the Mn-O bond in the Raman spectrum of the positive electrode active material is 80 cm -1 to 95 cm -1 .

[0012] In one embodiment, when the values of the same M element and y, z are the same, compared with Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d , the change rate of the unit cell parameter of the positive electrode active material is less than or equal to -0.04%.

[0013] In one embodiment, the crystal structure of the positive electrode active material includes single crystal and / or polycrystal.

[0014] In one embodiment, the particle size of the single crystal is 0.5 μm to 30 μm;

[0015] and / or, the particle size of the polycrystal is 0.1 μm to 20 μm.

[0016] A method for preparing a positive electrode active material as described above, comprising the following steps: x

[0017] Based on Li 1+a Na x P y Ni 0.5+b Mn 1.5+c M z O d , -0.1 ≤ a ≤ 0.2, -0.2 ≤ b ≤ 0.2, -0.2 ≤ c ≤ 0.2, 3.8 ≤ d ≤ 4.3, 0 < x ≤ 0.15, 0 < y ≤ 0.1, 0 ≤ z ≤ 0.2, mix the nickel-manganese hydroxide precursor with a lithium source and a doping source and then perform a sintering treatment to obtain the positive electrode active material, wherein the doping source includes a sodium source and a phosphorus source, or the doping source includes a sodium source, a phosphorus source and a compound containing an M element.

[0018] In one embodiment, the preparation method satisfies at least one of the following conditions:

[0019] (1) The chemical formula of the nickel-manganese hydroxide precursor is Ni 0.5+b Mn 1.5+c (OH) e , where, -0.2 ≤ b ≤ 0.2, -0.2 ≤ c ≤ 0.2, 3.8 ≤ e ≤ 4.2;

[0020] (2) The lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium nitrate, lithium citrate or lithium fluoride;

[0021] (3) The sodium source is selected from at least one of sodium-containing phosphates, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxalate, sodium nitrate, sodium citrate, sodium fluoride, sodium chloride, sodium sulfate, or sodium oxide;

[0022] (4) The phosphorus source is selected from at least one of sodium-containing phosphates, M-containing phosphates, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium pyrophosphate, pyrophosphoric acid, orthophosphoric acid, phosphorus pentoxide, or elemental phosphorus.

[0023] In one embodiment, the sintering process is performed at a temperature of 900° C. to 1050° C. and for a time of 1 hour to 30 hours.

[0024] In one embodiment, after the sintering process, an annealing process is further included, wherein the annealing process is performed at a temperature of 500° C. to 800° C. and for a time of 1 hour to 10 hours.

[0025] A positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode active material as described above.

[0026] A lithium-ion battery comprises the positive electrode sheet described above.

[0027] In one embodiment, the charging capacity of the lithium-ion battery below 4.4V in the first cycle accounts for less than 6% of the total charging capacity in the first cycle.

[0028] An electrical device comprises the lithium-ion battery described above.

[0029] The positive electrode active material described in the present application is co-doped with Na and P, wherein part of Na is doped into the transition metal layer, which can effectively suppress the problem of increased disorder of P-doped lithium nickel manganese oxide. It can not only reduce the proportion of charging platforms of lithium nickel manganese oxide below 4V, significantly increase the average voltage, greatly reduce the polarization voltage between charge and discharge, make the charge and discharge curve show excellent platform characteristics and reversible characteristics, improve energy density, but also effectively improve the rate performance of P-doped lithium nickel manganese oxide.

[0030] Compared with the traditional long-term heat preservation annealing method, the present application achieves Na and P co-doping of lithium nickel manganese oxide through a simple one-time sintering. Not only is the preparation method simple and fast, and can achieve a better effect of reducing disorder than the traditional long-term heat preservation annealing method, but it can also significantly shorten the preparation time of lithium nickel manganese oxide, thereby reducing energy consumption and reducing costs.

[0031] Therefore, using the positive electrode active material described in this application in lithium-ion batteries is beneficial to reducing the preparation cost of lithium nickel manganese oxide, increasing the energy density of lithium nickel manganese oxide, and thus improving the overall cost-effectiveness of lithium nickel manganese oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] FIG1 is a scanning electron microscope image of the positive electrode active material prepared in Example 1;

[0034] FIG2 is a scanning electron microscope image of the positive electrode active material prepared in Comparative Example 1;

[0035] FIG3 is a comparison of Raman spectra of the positive electrode active materials obtained in Example 3 and Comparative Example 1, wherein A is the Raman spectrum of the positive electrode active material obtained in Example 3, and B is the Raman spectrum of the positive electrode active material obtained in Comparative Example 1;

[0036] Figure 4 is a first-cycle charge and discharge curve diagram, wherein A is the first-cycle charge and discharge curve of Example 1, B is the first-cycle charge and discharge curve of Example 2, C is the first-cycle charge and discharge curve of Example 3, D is the first-cycle charge and discharge curve of Example 4, E is the first-cycle charge and discharge curve of Example 5, and F is the first-cycle charge and discharge curve of Comparative Example 1. DETAILED DESCRIPTION

[0037] To facilitate understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments or embodiments and are not intended to limit the present application. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0039] This application provides a positive electrode active material, and the chemical formula of the positive electrode active material is Li 1+a Na x P y Ni 0.5+b Mn 1.5+c M z O d , where -0.1 ≤ a ≤ 0.2, -0.2 ≤ b ≤ 0.2, -0.2 ≤ c ≤ 0.2, 3.8 ≤ d ≤ 4.3, 0 < x ≤ 0.15, 0 < y ≤ 0.1, 0 ≤ z ≤ 0.2, and the M element is selected from at least one of Mg, Al, Ca, Sc, Ti, V, Cr, Fe, Co, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, S or F.

[0040] The positive electrode active material described in this application has co-doping of Na and P. Among them, part of the Na is doped into the transition metal layer, which can effectively inhibit the problem of increased disorder degree of P-doped lithium nickel manganate. It can not only reduce the proportion of the charging platform below 4V of lithium nickel manganate, significantly improve the average voltage, greatly reduce the polarization voltage between charge and discharge, make the charge-discharge curve show excellent platform characteristics and reversible characteristics, improve the energy density, but also effectively improve the rate performance of P-doped lithium nickel manganate.

[0041] Preferably, the M element is selected from at least one of Ti, V, Ta, Nb, Mo, Ta, W, Te.​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The disorder degree is defined by the difference between the charge capacity of the positive electrode active material below 4.4V in the first cycle. Specifically, under the same y value, Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d The proportion of the charge capacity below 4.4V in the first cycle to the total charge capacity of the first cycle is defined as W1, and the proportion of the charge capacity of the positive electrode active material below 4.4V in the first cycle to the total charge capacity of the first cycle is defined as W2, then the disorder σ=(W2-W1) / W1, σ≤-15%, where the same y and z values ​​refer to Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d The values ​​of y and z of the two in the positive electrode active material are within a 5% error range, and this application does not limit Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d The values ​​of a, b, c, and d are the same as those in the positive electrode active material, and the difference rate of a between the two values ​​fluctuates within 20%, the difference rate of b values ​​fluctuates within 5%, the difference rate of c values ​​fluctuates within 5%, and the difference rate of d values ​​fluctuates within 6%, which are all feasible.

[0045] In one embodiment, the half-peak width of the main peak of the Ni-O bond of the positive electrode active material in the Raman spectrum is 30 cm -1 Up to 55cm -1 .

[0046] In one embodiment, the half-peak width of the main peak of the Mn-O bond of the positive electrode active material in the Raman spectrum is 80 cm -1 Up to 95cm -1 .

[0047] It should be noted that the positive electrode active material is located at 480 cm in the Raman spectrum. -1 The resonance peak near the Ni-O bond is mainly located at 625 cm -1 The resonance peaks nearby are mainly the main peaks of Mn-O bonds.

[0048] Li with the same y value 1+a P y Ni 0.5+b Mn 1.5+c M z O dIn comparison, the half-peak width of the Ni-O bond and the half-peak width of the Mn-O bond of the positive electrode active material of the present application are reduced by 4.5 cm -1 The above is because part of the Na in the positive electrode active material is doped into the transition metal layer, which effectively suppresses the increase in disorder of P-doped lithium nickel manganese oxide, improves the orderliness of the positive electrode active material, and enables the positive electrode active material to have both good energy density and rate performance.

[0049] In the positive electrode active material described in this application, a portion of Na is doped into the transition metal site to shrink the lattice, and another portion of Na is doped into the lithium site to expand the lattice. Under the same M element and y, z values, the same as Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d In contrast, when Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d When the unit cell parameter of the positive electrode active material is α1 and the unit cell parameter of the positive electrode active material is α2, the change rate of the unit cell parameter of the positive electrode active material γ=(α2-α1) / α1. Preferably, the change rate of the unit cell parameter of the positive electrode active material is less than or equal to -0.04%, wherein the same y and z values ​​refer to Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d The values ​​of y and z of the two in the positive electrode active material are within a 5% error range, and this application does not limit Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d The values ​​of a, b, c, and d are the same as those in the positive electrode active material, and the difference rate of a between the two values ​​fluctuates within 20%, the difference rate of b values ​​fluctuates within 5%, the difference rate of c values ​​fluctuates within 5%, and the difference rate of d values ​​fluctuates within 6%, which are all feasible.

[0050] In one embodiment, the positive electrode active material has a crystal structure including single crystal and / or polycrystalline.

[0051] The single crystal preferably has a particle size of 0.5 μm to 30 μm, preferably 1 μm to 10 μm.

[0052] The grain size of the polycrystal is preferably 0.1 μm to 20 μm, more preferably 1 μm to 10 μm.

[0053] It should be noted that the surface of the positive electrode active material may also have a coating layer, and the present application does not limit the type of the coating layer, and all types of coating layers involved in the prior art can be applied.

[0054] The present application provides a method for preparing the positive electrode active material as described above, including the following steps:

[0055] Based on Li 1+a Na x P y Ni 0.5+b Mn 1.5+c M z O d , -0.1≤a≤0.2, -0.2≤b≤0.2, -0.2≤c≤0.2, 3.8≤d≤4.3, 0<x≤0.15, 0<y≤0.1, 0≤z≤0.2, the nickel-manganese hydroxide precursor is mixed with a lithium source and a doping source and then sintered to obtain the positive electrode active material, wherein the doping source includes a sodium source and a phosphorus source, or the doping source includes a sodium source, a phosphorus source and a compound containing element M.

[0056] Compared with the traditional long-time heat preservation annealing method, the present application realizes the co-doping of Na and P in lithium nickel manganate through simple one-time sintering. Not only is the preparation method simple and fast, and the effect of reducing the degree of disorder is better than that of the traditional long-time heat preservation annealing method, but also the preparation time of lithium nickel manganate can be greatly shortened, thereby reducing energy consumption and cost.

[0057] In one embodiment, the chemical formula of the nickel-manganese hydroxide precursor is Ni 0.5+b Mn 1.5+c (OH) e , wherein, -0.2≤b≤0.2, -0.2≤c≤0.2, 3.8≤e≤4.2.

[0058] It should be noted that the present application does not limit the preparation method of the nickel-manganese hydroxide precursor, and it can be prepared by using existing technologies such as the coprecipitation method, etc., and the present application will not elaborate on this.

[0059] In one embodiment, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium nitrate, lithium citrate or lithium fluoride, and lithium carbonate or lithium hydroxide is preferred. <^

[0060] In one embodiment, the sodium source is selected from at least one of sodium-containing phosphates, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxalate, sodium nitrate, sodium citrate, sodium fluoride, sodium chloride, sodium sulfate or sodium oxide, and at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxalate is preferred.

[0061] In one embodiment, the phosphorus source is selected from at least one of sodium-containing phosphates, M-containing phosphates, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium pyrophosphate, pyrophosphoric acid, orthophosphoric acid, phosphorus pentoxide, or elemental phosphorus.

[0062] The sodium-containing phosphate is selected from at least one of sodium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, trisodium pyrophosphate, trisodium monohydrogen pyrophosphate and disodium dihydrogen pyrophosphate.

[0063] The phosphate containing the M element is selected from at least one of nickel phosphate, cobalt phosphate, manganese phosphate, magnesium phosphate, calcium phosphate, iron phosphate, copper phosphate, zinc phosphate, titanium phosphate, zirconium phosphate, lithium phosphate, cobalt pyrophosphate, nickel pyrophosphate, manganese pyrophosphate, magnesium pyrophosphate, calcium pyrophosphate, iron pyrophosphate, copper pyrophosphate, zinc pyrophosphate, titanium pyrophosphate or zirconium pyrophosphate.

[0064] Preferably, the phosphorus source is selected from at least one of ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium pyrophosphate, pyrophosphoric acid, orthophosphoric acid, phosphorus pentoxide, elemental phosphorus, nickel phosphate or manganese phosphate.

[0065] It should be noted that when the sodium source is selected from a phosphate containing the sodium element, since the sodium source contains a phosphorus source, there is no need to add other phosphorus sources; when the phosphorus source is selected from a phosphate containing the sodium element, since the phosphorus source contains a sodium source, there is no need to add other sodium sources; when the phosphorus source is selected from a phosphate containing the M element, since the phosphorus source includes a compound containing the M element, there is no need to add other compounds containing the M element.

[0066] In one embodiment, the sintering treatment is performed at a temperature of 900° C. to 1050° C., preferably 920° C. to 1000° C., and for a time of 1 hour to 30 hours, preferably 5 hours to 20 hours.

[0067] In another embodiment, after the sintering treatment, an annealing treatment is also included. The annealing treatment temperature is 500°C to 800°C, preferably 600°C to 700°C; the time is 1h to 10h, preferably 3h to 6h. Through a short annealing treatment, it is beneficial to further suppress the increase in disorder of P-doped lithium nickel manganese oxide and improve the orderliness.

[0068] The present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer disposed on a surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode active material as described above.

[0069] In one embodiment, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector includes a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate. Optionally, the metal material includes but is not limited to one or more of aluminum, aluminum gold, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. Optionally, the polymer material substrate includes but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0070] In one embodiment, the positive electrode material layer is primarily composed of the positive electrode active material described herein, a binder, and a conductive agent. Optionally, the conductive agent includes, but is not limited to, at least one of carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, wherein the carbon black includes superconducting carbon, acetylene black, or Ketjen black.

[0071] It should be noted that this application does not limit the preparation method of the positive electrode sheet, and conventional processes can be used for preparation. For example, the positive electrode active material, conductive agent, binder, and any other components are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet can be obtained. Optionally, the solvent includes but is not limited to N-methylpyrrolidone.

[0072] The present application provides a lithium-ion battery, comprising the positive electrode sheet as described above.

[0073] The lithium-ion battery is mainly composed of a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the negative electrode sheet, the separator and the electrolyte can adopt any conventional commercially available negative electrode sheet (or negative electrode material), the separator and the electrolyte, and this application does not impose any limitation on this.

[0074] In one embodiment, the smaller the proportion of the charging capacity of the lithium ion battery below 4.4V in the first cycle in the total charging capacity of the first cycle, the longer the platform and the larger the average voltage. Specifically, under the conditions of an electrochemical window of 3.5V to 4.95V and a nominal capacity of 150mAh / g, the battery is charged to 4.95V at a constant current of 0.1C and then charged to a current density of 0.05C at a constant voltage. Preferably, the proportion of the charging capacity of the lithium ion battery below 4.4V in the first cycle in the total charging capacity of the first cycle is less than 6%.

[0075] Based on this, under the same M element and y, z values, Li 1+a P y Ni 0.5+b Mn 1.5+c M z O dThe prepared lithium-ion battery, after charging under the electrochemical window of 3.5V to 4.95V and the nominal capacity of 150mAh / g, is discharged at a constant current of 0.1C to 3.5V, and the first cycle average discharge voltage obtained is defined as V1. The lithium-ion battery prepared by the positive electrode active material, after charging under the electrochemical window of 3.5V to 4.95V and the nominal capacity of 150mAh / g, is discharged at a constant current of 0.1C to 3.5V, and the first cycle average discharge voltage obtained is defined as V2. The change rate of the first cycle average discharge voltage of the lithium-ion battery prepared by the positive electrode active material of the present application is That is, the average first-cycle discharge voltage of the lithium-ion battery made from the positive electrode active material described in this application is increased by at least 1%.

[0076] The present application also provides an electrical device comprising the lithium-ion battery described above.

[0077] It is understandable that the above-mentioned power consumption settings include any equipment that uses the above-mentioned lithium-ion batteries, such as electric vehicles, power tools, electronic products, energy storage systems, and office equipment, but are not limited thereto.

[0078] The following specific examples further illustrate the positive electrode active material, its preparation method, and its application. However, those skilled in the art will understand that the following examples are merely illustrative of the present application and should not be construed as limiting the scope of the present application. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0079] Example 1

[0080] 1000g of Ni 0.5 Mn 1.5 The (OH)4 precursor, 5g of Ta2O5, 224g of lithium carbonate, 6.9g of sodium carbonate, and 39.6g of ammonium dihydrogen phosphate were added to a high-pressure mixer and stirred until uniform to obtain a mixture. The mixture was sintered at 950°C for 15 hours, then cooled at a rate of 0.5°C / min to 650°C, then held at 650°C for 4 hours. After natural cooling, the mixture was crushed and sieved to obtain the positive electrode active material. A scanning electron microscope image of the positive electrode active material prepared in this example is shown in Figure 1.

[0081] Example 2

[0082] The difference between Example 2 and Example 1 is that the amount of lithium carbonate is 220.8 g and the amount of sodium carbonate is 11.5 g.

[0083] Example 3

[0084] The difference between Example 3 and Example 1 is that the amount of lithium carbonate is 217.6 g and the amount of sodium carbonate is 16.1 g.

[0085] Example 4

[0086] The difference between Example 4 and Example 1 is that the amount of lithium carbonate is 214.3 g and the amount of sodium carbonate is 20.7 g.

[0087] Example 5

[0088] The difference between Example 5 and Example 1 is that the amount of lithium carbonate is 204.7 g and the amount of sodium carbonate is 34.6 g.

[0089] Example 6

[0090] 1000g of Ni 0.5 Mn 1.5 The (OH)4 precursor, 8g of TiO2, 208.4g of lithium carbonate, 2.3g of sodium carbonate, and 3.86g of ammonium dihydrogen phosphate were added to a high-speed mixer and stirred until uniform to obtain a mixture. The mixture was sintered at 970°C for 15h, then cooled at 0.5°C / min to 650°C, and then held at 650°C for 4h. After natural cooling, the mixture was crushed and sieved to obtain the positive electrode active material.

[0091] Example 7

[0092] The difference between Example 7 and Example 6 is that the amount of lithium carbonate is 210.7 g, the amount of sodium carbonate is 6.9 g, and the amount of ammonium dihydrogen phosphate is 11.63 g.

[0093] Example 8

[0094] The difference between Example 8 and Example 6 is that the amount of lithium carbonate is 210.9 g, the amount of sodium carbonate is 11.5 g, and the amount of ammonium dihydrogen phosphate is 19.50 g.

[0095] Example 9

[0096] The difference between Example 9 and Example 6 is that the amount of lithium carbonate is 211.2 g, the amount of sodium carbonate is 16.1 g, and the amount of ammonium dihydrogen phosphate is 27.47 g.

[0097] Example 10

[0098] The difference between Example 10 and Example 6 is that the amount of lithium carbonate is 211.5 g, the amount of sodium carbonate is 20.7 g, and the amount of ammonium dihydrogen phosphate is 35.53 g.

[0099] Example 11

[0100] The difference between Example 11 and Example 6 is that the amount of lithium carbonate is 211.9 g, the amount of sodium carbonate is 25.3 g, and the amount of ammonium dihydrogen phosphate is 43.4 g.

[0101] Example 12

[0102] The difference between Example 12 and Example 6 is that the amount of lithium carbonate is 212.2 g, the amount of sodium carbonate is 29.9 g, and the amount of ammonium dihydrogen phosphate is 54.7 g.

[0103] Example 13

[0104] 1000g of Ni 0.5 Mn 1.5 The (OH)4 precursor, 8g of TiO2, 210.9g of lithium carbonate, 11.5g of sodium carbonate, and 19.5g of ammonium dihydrogen phosphate were added to a high-speed mixer and stirred until uniform to obtain a mixture. The mixture was sintered at 970°C for 15h, then cooled at 0.5°C / min to 650°C. After natural cooling, it was crushed and sieved to obtain the positive electrode active material.

[0105] Example 14

[0106] The difference between Example 14 and Example 13 is that the amount of lithium carbonate is 211.2 g, the amount of sodium carbonate is 16.1 g, and the amount of ammonium dihydrogen phosphate is 27.5 g.

[0107] Example 15

[0108] 1000g of Ni 0.5 Mn 1.5 The (OH)4 precursor, 8g of Al2O3, 2g of Nb2O5, 208.4g of lithium carbonate, and 14.5g of sodium pyrophosphate decahydrate were added to a high-pressure mixer and stirred until uniform to obtain a mixture. The mixture was sintered at 930°C for 15h, then cooled at a rate of 0.5°C / min to 650°C, then held at 650°C for 4h. After natural cooling, the mixture was crushed and sieved to obtain the positive electrode active material.

[0109] Example 16

[0110] The difference between Example 16 and Example 15 is that Nb2O5 is 2 g, lithium carbonate is 207.7 g, and sodium pyrophosphate decahydrate is 24.2 g.

[0111] Example 17

[0112] The difference between Example 17 and Example 15 is that Nb2O5 is 2 g, lithium carbonate is 207.5 g, and sodium pyrophosphate decahydrate is 33.9 g.

[0113] Example 18

[0114] The difference between Example 18 and Example 15 is that Nb2O5 is 2 g, lithium carbonate is 207.3 g, and sodium pyrophosphate decahydrate is 43.6 g.

[0115] Example 19

[0116] The difference between Example 19 and Example 15 is that Nb2O5 is 2 g, lithium carbonate is 207.3 g, and sodium pyrophosphate decahydrate is 72.7 g.

[0117] Comparative Example 1

[0118] 1000g of Ni 0.5 Mn 1.5 The (OH)4 precursor, 5g of Ta2O5, 228.8g of lithium carbonate, and 39.6g of ammonium dihydrogen phosphate were added to a high-speed mixer and stirred until homogeneous to obtain a mixture. The mixture was sintered at 950°C for 15 hours, then cooled at a rate of 0.5°C / min to 650°C, then held at 650°C for 4 hours. After natural cooling, the mixture was crushed and sieved to obtain the positive electrode active material. A scanning electron microscope image of the positive electrode active material prepared in this comparative example is shown in Figure 2.

[0119] Comparative Example 2

[0120] The difference between Comparative Example 2 and Example 6 is that no sodium carbonate was added and the amount of lithium carbonate was 210.1 g.

[0121] Comparative Example 3

[0122] The difference between Comparative Example 3 and Example 7 is that no sodium carbonate was added and the amount of lithium carbonate was 215.5 g.

[0123] Comparative Example 4

[0124] The difference between Comparative Example 4 and Example 8 is that no sodium carbonate was added and the amount of lithium carbonate was 218.9 g.

[0125] Comparative Example 5

[0126] The difference between Comparative Example 5 and Example 9 is that no sodium carbonate was added and the amount of lithium carbonate was 222.4 g.

[0127] Comparative Example 6

[0128] The difference between Comparative Example 6 and Example 10 is that no sodium carbonate was added and the amount of lithium carbonate was 225.9 g.

[0129] Comparative Example 7

[0130] The difference between Comparative Example 7 and Example 11 is that no sodium carbonate was added and the amount of lithium carbonate was 231.7 g.

[0131] Comparative Example 8

[0132] The difference between Comparative Example 8 and Example 12 is that no sodium carbonate was added and the amount of lithium carbonate was 237.5 g.

[0133] Comparative Example 9

[0134] The difference between Comparative Example 9 and Example 13 is that no sodium carbonate was added and the amount of lithium carbonate was 218.9 g.

[0135] Comparative Example 10

[0136] The difference between Comparative Example 10 and Example 14 is that no sodium carbonate was added and the amount of lithium carbonate was 222.4 g.

[0137] Comparative Example 11

[0138] The difference between Comparative Example 11 and Example 15 is that 14.5 g of sodium pyrophosphate decahydrate is replaced by 7.84 g of ammonium dihydrogen phosphate, and the amount of lithium carbonate is 216.2 g.

[0139] Comparative Example 12

[0140] The difference between Comparative Example 12 and Example 16 is that 24.2 g of sodium pyrophosphate decahydrate is replaced by 13.12 g of ammonium dihydrogen phosphate, and the amount of lithium carbonate is 219.2 g.

[0141] Comparative Example 13

[0142] The difference between Comparative Example 13 and Example 17 is that 33.9 g of sodium pyrophosphate decahydrate is replaced by 18.45 g of ammonium dihydrogen phosphate, and the amount of lithium carbonate is 222.3 g.

[0143] Comparative Example 14

[0144] The difference between Comparative Example 14 and Example 18 is that 43.6 g of sodium pyrophosphate decahydrate is replaced by 23.85 g of ammonium dihydrogen phosphate and 227.5 g of lithium carbonate.

[0145] Comparative Example 15

[0146] The difference between Comparative Example 15 and Example 19 is that 72.7 g of sodium pyrophosphate decahydrate is replaced by 40.30 g of ammonium dihydrogen phosphate, and the amount of lithium carbonate is 239.0 g.

[0147] The positive electrode active materials prepared in Examples 1 to 19 and Comparative Examples 1 to 15 were characterized, and the results are shown in FIG3 and Tables 1 and 2. It should be noted that there is a reasonable calculation error between the measured chemical formula in Table 1 and the theoretical chemical formula.

[0148] Table 1

[0149] Table 2

[0150] Figure 3 is the Raman spectra of Example 3 and Comparative Example 1, 390 cm -1 、480cm -1The peaks near this point are mainly the Ni-O bond resonance peaks in lithium nickel manganese oxide, 625 cm -1 The peak near this is the Mn-O bond resonance peak in lithium nickel manganese oxide. According to Figure 3, Table 1 and Table 2, the Na-P co-doped sample of Example 3 is located at 480 cm -1 The Ni-O bond near 625 cm -1 The half-peak width of the Mn-O bond near the 390cm-1 peak is significantly lower than that of the P-doped sample in Comparative Example 1. -1 The Ni-O bond near the surface is a typical peak structure, while the comparative example 1 is a diffuse peak, and the embodiment 3 is at 210cm -1 There are typical characteristic peaks near . These all indicate that Example 3 has lower disorder than Comparative Example 1. As can be seen from Table 1 and Table 2, the half-peak widths of the Na-P co-doped samples are significantly lower than those of the corresponding P-doped samples, indicating that Na-P co-doping can significantly reduce the disorder of lithium nickel manganese oxide.

[0151] According to classical crystallographic knowledge, since the radius of Na ions is significantly larger than that of Li ions, if Na ions completely replace Li ions, the lattice of the material will expand, which is manifested as an increase in the unit cell parameters. However, in this patent application, it can be seen from Tables 1 and 2 that after Na doping, the unit cell parameters of lithium nickel manganese oxide decrease and the lattice shrinks, proving that Na ions are partially doped into Ni and Mn sites, so the chemical formula is Li 1+a Na x P y Ni 0.5+b Mn 1.5+c M z O d .

[0152] The positive electrode active materials prepared in Examples 1 to 19 and Comparative Examples 1 to 15 were used to prepare button batteries in sequence. The specific preparation steps were as follows: the positive electrode material: Super P: PVDF = 94.5:3:3.5 ratio was used to prepare the electrode slurry, and the surface loading was 10 mg / cm 2 After drying, the positive electrode sheet was obtained. The positive electrode sheet and the metal lithium negative electrode were assembled into a CR2430 button battery for testing.

[0153] The performance of the prepared button battery was tested using a constant current and constant voltage charging + constant current discharge mode at a current density of 0.1C (nominal capacity 150mAh / g). The test results are shown in Figure 4 and Table 3, where W is the proportion of the charging capacity below 4.4V in the first cycle to the total charging capacity in the first cycle; σ is the degree of disorder; is the rate of change of the average discharge voltage in the first cycle.

[0154] Table 3

[0155] Figure 4 shows the charge-discharge curves for Examples 1 to 6. It clearly shows that, at the same P doping level, increasing the Na doping level leads to a significant upward shift in the discharge curve and a higher voltage. Table 3 shows that the disorder of the Na-P co-doped samples is significantly lower than that of the corresponding P-doped samples, indicating that Na-P co-doping can significantly improve the order of lithium nickel manganese oxide and increase the average discharge voltage.

[0156] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0157] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A positive electrode active material, wherein The chemical formula of the positive electrode active material is Li 1+a Na x P y Ni 0.5+b Mn 1.5+c M z O d , where -0.1 ≤ a ≤ 0.2, -0.2 ≤ b ≤ 0.2, -0.2 ≤ c ≤ 0.2, 3.8 ≤ d ≤ 4.3, 0 < x ≤ 0.15, 0 < y ≤ 0.1, 0 ≤ z ≤ 0.2, and the M element is selected from at least one of Mg, Al, Ca, Sc, Ti, V, Cr, Fe, Co, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, S, or F.

2. The positive electrode active material according to claim 1, wherein Under the same M element and y, z values, Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d In comparison, the disorder degree of the positive electrode active material is reduced by at least 15%.

3. The positive electrode active material according to claim 1, wherein The half-peak width of the main peak of the Ni-O bond of the positive electrode active material in the Raman spectrum is 30 cm -1 Up to 55cm -1 .

4. The positive electrode active material according to claim 1, wherein The half-peak width of the main peak of the Mn-O bond of the positive electrode active material in the Raman spectrum is 80 cm -1 Up to 95cm -1 .

5. The positive electrode active material according to claim 1, wherein Under the same M element and y, z values, Li 1+a P y Ni 0.5+b Mn 1.5+c M z O d In comparison, the change rate of the unit cell parameter of the positive electrode active material is less than or equal to -0.04%.

6. The positive electrode active material according to claim 1, wherein The crystal structure of the positive electrode active material includes single crystal and / or polycrystal.

7. The positive electrode active material according to claim 6, wherein The particle size of the single crystal is 0.5 μm to 30 μm; And / or, the grain size of the polycrystal is 0.1 μm to 20 μm.

8. A method for preparing a positive electrode active material according to any one of claims 1 to 7, wherein: The steps include: Taking Li 1+a Na x P y Ni 0.5+b Mn 1.5+c M z O d as a reference, where -0.1 ≤ a ≤ 0.2, -0.2 ≤ b ≤ 0.2, -0.2 ≤ c ≤ 0.2, 3.8 ≤ d ≤ 4.3, 0 < x ≤ 0.15, 0 < y ≤ 0.1, 0 ≤ z ≤ 0.2, the nickel-manganese hydroxide precursor is mixed with a lithium source and a doping source and then sintered to obtain the positive electrode active material, wherein the doping source includes a sodium source and a phosphorus source, or the doping source includes a sodium source, a phosphorus source and a compound containing element M.

9. The method for preparing a positive electrode active material according to claim 8, wherein: The preparation method satisfies at least one of the following conditions: (1) The chemical formula of the nickel manganese hydroxide precursor is Ni 0.5+b Mn 1.5+c (OH) e , where -0.2≤b≤0.2, -0.2≤c≤0.2, 3.8≤e≤4.2; (2) The lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium nitrate, lithium citrate or lithium fluoride; (3) The sodium source is selected from at least one of sodium-containing phosphates, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxalate, sodium nitrate, sodium citrate, sodium fluoride, sodium chloride, sodium sulfate or sodium oxide; (4) The phosphorus source is selected from at least one of sodium-containing phosphates, M-containing phosphates, ammonium phosphate, diammonium phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium pyrophosphate, pyrophosphoric acid, orthophosphoric acid, phosphorus pentoxide or elemental phosphorus.

10. The method for preparing a positive electrode active material according to claim 8, wherein: The sintering process is performed at a temperature of 900° C. to 1050° C. and for a time of 1 hour to 30 hours.

11. The method for preparing a positive electrode active material according to claim 8, wherein: After the sintering process, an annealing process is further included, wherein the annealing process is performed at a temperature of 500° C. to 900° C. and for a time of 1 hour to 10 hours.

12. A positive electrode sheet, wherein: The invention comprises a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode active material according to any one of claims 1 to 7.

13. A lithium ion battery, wherein: Comprising the positive electrode sheet as claimed in claim 12.

14. The lithium ion battery according to claim 13, wherein: The charging capacity of the lithium-ion battery below 4.4V in the first cycle accounts for less than 6% of the total charging capacity in the first cycle.

15. An electrical device, wherein: Comprising a lithium ion battery as claimed in claim 13 or claim 14.

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