Positive electrode material, preparation method thereof and battery

Abstract

The invention relates to the field of new energy batteries, in particular to a positive electrode material, a preparation method thereof and a battery, the positive electrode material comprises a layered oxide positive electrode material and a coating layer coating the surface of the layered oxide positive electrode material; the material of the coating layer comprises phosphate; wherein the layered oxide positive electrode material comprises NawNixFeyMnzZnpCaqOmFn, x + y + z + p + q = 1, 0.2 < = x < = 0.4, 0.2 < = y < = 0.33, 0.3 < = z < = 0.4, 0.03 < = p < = 0.1, 0 < q < = 0.01, 0 < n < = 0.4, 1.8 < = m < = 2.2, and 0.8 < = w < = 1.2. The positive electrode material disclosed by the invention has remarkably improved stability under the conditions of high magnification and long circulation.

Description

Technical Field

[0001] The present invention relates to the field of new energy batteries, and specifically, to a cathode material, a preparation method thereof, and a battery. Background Art

[0002] The layered oxide Na x TMO 2 (TM = transition metal) has component diversity and controllability, and has great research value. At present, the main problems of the zinc-based sodium nickel iron manganese oxide cathode material for sodium-ion batteries include: poor air stability, increasing the zinc content to increase the specific capacity of the material leads to metal ion dissolution and obvious deterioration of the cycle, and side reactions consume the electrolyte and active substances, which are aggravated. These problems will ultimately lead to a decrease in battery capacity and deterioration of the cycle, etc., thus making the commercial progress of the zinc-based sodium-ion layered oxide cathode material slow.

[0003] Currently, the main methods to improve the structural stability of materials are: the synergistic effect of multi-element doping, and multi-elements are doped into the lattice of the cathode material through solid-phase sintering or precursor doping. Patent document CN114204028A discloses a sodium-ion battery cathode material coated with a polymer material, but using only a polymer material coating will affect the ionic conductivity of the material, reduce the rate performance, cycle stability and capacity performance of the material. Summary of the Invention

[0004] In view of this, the present invention is committed to providing a cathode material, a preparation method thereof, and a battery to solve the problems of poor structural stability and cycle stability of the zinc-based sodium-ion cathode material in the prior art.

[0005] To solve the above technical problems, the present invention is implemented as follows:

[0006] The first aspect of the present invention provides a cathode material, which includes a layered oxide cathode material and a coating layer coated on the surface of the layered oxide cathode material;

[0007] The material of the coating layer includes phosphate;

[0008] Among them, the layered oxide cathode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n, where x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 0.8 ≤ w ≤ 1.2.

[0009] Optionally, the layered oxide cathode material includes a P2-type layered oxide cathode material, where the P2-type layered oxide cathode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 0.8 ≤ w ≤ 1.0; alternatively, the layered oxide cathode material includes an O3-type layered oxide cathode material, where the O3-type layered oxide cathode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 1.0 < w ≤ 1.2; the phosphate includes manganese phosphate and / or sodium manganese phosphate.

[0010] Optionally, the D50 of the layered oxide cathode material is 6.0 - 9.0 μm, preferably 7.2 - 7.8 μm; based on the total mass of the cathode material, the content of the layered oxide cathode material is 95 - 99.9 wt%, preferably 99 - 99.5 wt%.

[0011] Optionally, the thickness of the coating layer is 5 - 20 nm, preferably 8 - 12 nm.

[0012] The second aspect of the present invention provides a method for preparing a cathode material, and the preparation method includes the following steps:

[0013] (1) Mix the layered oxide cathode material with a first precursor and perform a first atomic deposition treatment to obtain a first material;

[0014] (2) Mix the first material with the second precursor and perform a second atomic deposition treatment to obtain a second material;

[0015] (3) Repeat steps (1) and (2) successively 5 to 60 times;

[0016] Among them, the layered oxide cathode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 0.8 < w < 1.2;

[0017] The first precursor includes ethylcyclopentadienylmanganese; the second precursor includes trimethyl phosphate.

[0018] Optionally, the mass ratio of the layered oxide cathode material to the first precursor in the mixing is 1:0.0001 to 0.01; the mass ratio of the first material to the second precursor in the mixing is 1:0.3 to 0.6; the conditions for the first atomic deposition treatment include: temperature is 80 to 200 °C, pressure is 1×10 -5 MPa, time is 10 to 30 min; the conditions for the second atomic deposition treatment include: temperature is 80 to 200 °C, pressure is 1×10 -5 MPa, time is 10 to 30 min; the number of repetitions of steps (1) and (2) is 5 - 20 times.

[0019] Optionally, the preparation method further includes: mixing a sodium source, a nickel source, an iron source, a manganese source, a zinc source, a calcium source, and a fluorine source to obtain a mixture powder; calcining the mixture powder to obtain the layered oxide cathode material; optionally, the molar ratio of the sodium source, the nickel source, the iron source, the manganese source, the zinc source, the calcium source, and the fluorine source in the mixing is (2 - 4):(2 - 3.3):(3 - 4):(0.3 - 1):(0 - 0.1):(0 - 4):(18 - 22).

[0020] Optionally, the sodium source includes at least one of sodium carbonate, sodium acetate, sodium nitrate, and sodium hydroxide; the nickel source includes at least one of nickel oxide, nickel acetate, nickel nitrate, and nickel hydroxide; the iron source includes at least one of iron(III) oxide, iron acetate, iron nitrate, and iron hydroxide; the manganese source includes at least one of manganese dioxide, manganese acetate, manganese nitrate, and manganese hydroxide; the zinc source includes at least one of zinc oxide, zinc acetate, zinc nitrate, and zinc hydroxide; the calcium source includes at least one of calcium oxide, calcium acetate, calcium nitrate, and calcium hydroxide; the fluorine source includes sodium fluoride and / or ammonium fluoride.

[0021] Optionally, the mixing treatment is ball milling, and the conditions of the ball milling treatment include: the mixing temperature is 40 - 80°C, the mixing time is 4 - 10 h, and the mixing rotation speed is 200 - 600 rpm / min; the conditions of the calcination treatment include: the calcination temperature is 600 - 1000°C, and the calcination time is 360 - 600 min.

[0022] The third aspect of the present invention provides a battery, which includes a positive electrode sheet containing a positive electrode active material. Among them, the positive electrode active material includes the above-mentioned positive electrode material and / or the positive electrode material prepared according to the above-mentioned preparation method.

[0023] Through the above technical solutions, the beneficial technical effects of the present invention are as follows:

[0024] (1) The positive electrode material of the present invention includes a layered oxide positive electrode material and a coating layer coated on the surface of the layered oxide positive electrode material. Among them, the layered oxide positive electrode material introduces calcium and fluoride ions into the bulk structure to play a synergistic role. Ca 2+ has an ionic radius similar to that of Na + and can replace the sodium site, enhancing the interlayer stability of the material and the stability of the sodium-depleted state; the introduction of F - replaces part of the oxygen, and further enhances the structural stability of the material due to its strong electronegativity.

[0025] (2) The positive electrode material of the present invention has a phosphate coating layer with a uniform nano-thickness, which improves the interface stability of the material and prevents side reactions between the active substance and the electrolyte; at the same time, a small amount of sodium phosphate solid electrolyte is generated, improving the material kinetics performance and enhancing the stability of the material under high rate and long cycle conditions.

[0026] (3) The preparation method of the present invention constructs a uniform ultra-thin coating layer with an atomic-level thickness (such as 5 - 20 nm) on the surface of primary particles through atomic layer deposition (ALD) technology; this coating layer improves the overall material kinetics performance and can also inhibit the occurrence of side reactions, achieving the effect of improving the interface stability of the material.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the following detailed implementation, they are used to explain the present invention, but do not constitute a limitation to the present invention.

[0029] Figure 1 Shown is the SEM image of the sodium - ion battery cathode material coated with manganese phosphate prepared in Example 1. DETAILED IMPLEMENTATION

[0030] The present invention discloses a cathode material, its preparation method and a battery. Those skilled in the art can draw on the content of this article and appropriately modify process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The methods and applications of the present invention have been described through preferred embodiments. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0031] In the description of the present invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0032] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values and individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] If there is no special instruction, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0034] If there is no special instruction, all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0035] Unless otherwise specified, the terms "comprising" and "including" mentioned in the present invention are open-ended and can also be closed-ended. For example, the terms "comprising" and "including" can mean that other components not listed may also be included or comprised, or it can mean that only the listed components are included or comprised.

[0036] In order to solve the problems of poor structural stability and cycling stability of zinc-based sodium battery cathode materials in the prior art, the present invention adopts the following technical solutions:

[0037] A first aspect of the present invention provides a cathode material, which includes a layered oxide cathode material and a coating layer coated on the surface of the layered oxide cathode material;

[0038] The material of the coating layer includes phosphate;

[0039] Among them, the layered oxide cathode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 0.8 ≤ w ≤ 1.2.

[0040] The cathode material of the present invention includes a layered oxide cathode material and a coating layer coated on the surface of the layered oxide cathode material. Among them, the layered oxide cathode material introduces calcium and fluoride ions into the bulk structure to play a synergistic role. Ca 2+ has an ionic radius similar to that of Na + and can replace the sodium site, enhancing the interlayer stability and the stability of the sodium-depleted state of the material; the introduction of F - replaces part of the oxygen, and further enhances the structural stability of the material due to its strong electronegativity; the phosphate coating layer on the surface of the layered oxide cathode material improves the interface stability of the material and prevents side reactions between the active material and the electrolyte; at the same time, a small amount of sodium phosphate solid electrolyte is generated, improving the kinetic performance of the material and enhancing the stability of the material under high rate and long cycle conditions.

[0041] In an exemplary embodiment of the present invention, the layered oxide cathode material includes a P2-type layered oxide cathode material, where the P2-type layered oxide cathode material includes Na w Ni x Fe y Mnz Zn p Ca q O m F n , wherein x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 0.8 ≤ w ≤ 1.0.

[0042] In another exemplary embodiment of the present invention, the layered oxide cathode material includes an O3-type layered oxide cathode material, wherein the O3-type layered oxide cathode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n , wherein x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 1.0 < w ≤ 1.2; the phosphate includes manganese phosphate and / or sodium manganese phosphate.

[0043] According to the present invention, the D50 of the suitable layered oxide cathode material can have the technical effects of improving the tap density and promoting the discharge capacity of the cathode material. The D50 of the layered oxide cathode material can be 6.0 - 9.0 μm. Exemplarily, the D50 of the layered oxide cathode material can be any value among 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, and 9 μm or any value within the range composed of any two of the above values. In the present invention, if the D50 of the layered oxide cathode material is too large, it may cause a decrease in the discharge capacity of the material; if the D50 of the layered oxide cathode material is too small, it may cause a decrease in the tap density. As a preferred embodiment of the present invention, the D50 of the layered oxide cathode material can be 7.2 - 7.8 μm.

[0044] According to the present invention, the content of the suitable layered oxide cathode material in the cathode material can have the technical effect of increasing the specific capacity of the cathode material and improving the rate performance of the material. Based on the total mass of the cathode material, the content of the layered oxide cathode material can be 95-99.9 wt%. Exemplarily, based on the total mass of the cathode material, the D50 of the content of the layered oxide cathode material can be any value among 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt% and 99.9 wt% or any value within the range value composed of any two of the above values. In the cathode material of the present invention, if the content of the layered oxide cathode material is too large, it may cause a decrease in the rate performance of the material; if the content of the layered oxide cathode material is too small, it may cause a decrease in the specific capacity of the cathode material. Preferably, based on the total mass of the cathode material, the D50 of the content of the layered oxide cathode material can be 99-99.5 wt%.

[0045] According to the present invention, the suitable thickness of the coating layer can have the technical effect of improving the cycle stability of the battery. The thickness of the coating layer can be 5-20 nm. Exemplarily, the thickness of the coating layer can be any value among 5 nm, 7 nm, 9 nm, 11 nm, 13 nm, 15 nm, 17 nm, 19 nm and 20 nm or any value within the range value composed of any two of the above values. In the present invention, if the thickness of the coating layer is too large, it may cause a decrease in the capacity of the battery; if the thickness of the coating layer is too small, it may cause a decrease in the cycle stability of the battery. As a preferred embodiment of the present invention, the thickness of the coating layer can be 8-12 nm.

[0046] The second aspect of the present invention provides a method for preparing a cathode material, and the preparation method includes the following steps:

[0047] (1) Mix the layered oxide cathode material with the first precursor and perform the first atomic deposition treatment to obtain the first material;

[0048] (2) Mix the first material with the second precursor and perform the second atomic deposition treatment to obtain the second material;

[0049] (3) Repeat steps (1) and (2) 5-60 times in sequence;

[0050] Wherein, the layered oxide cathode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n, where x + y + z + p + q = 1, 0.2 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.33, 0.3 ≤ z ≤ 0.4, 0.03 ≤ p ≤ 0.1, 0 < q ≤ 0.01, 0 < n ≤ 0.4, 1.8 ≤ m ≤ 2.2, 0.8 < w < 1.2;

[0051] The first precursor includes ethylmanganocene; the second precursor includes trimethyl phosphate.

[0052] The preparation method of the present invention constructs a uniform ultra-thin coating layer on the surface of primary particles through atomic layer deposition (ALD) technology, and the thickness is atomically regulated (for example, 5-20 nm); this coating layer improves the kinetic performance of the overall material and can also inhibit the occurrence of side reactions, achieving the effect of improving the interface stability of the material.

[0053] In an exemplary embodiment of the present invention, a first atomic deposition treatment and a second atomic deposition treatment can be carried out using the reaction chamber of an ALD device. For example, the first precursor is volatilized by heating and enters the reaction chamber, mixed with the layered oxide cathode material, and a first coating layer with a certain thickness is formed on the surface of the layered oxide cathode material to obtain a first material; the second precursor is volatilized by heating and enters the reaction chamber, mixed with the first material, and a second coating layer with a certain thickness is formed on the surface of the first material. The above steps are repeated multiple times until the target coating layer thickness is obtained. Exemplarily, the mass ratio of the layered oxide cathode material to the first precursor can be 1:0.0001-0.01; the mass ratio of the first material to the second precursor can be 1:0.3-0.6.

[0054] According to the present invention, the conditions for the first atomic deposition treatment can include: the temperature is 80-200 °C, the pressure is 1×10 -5 MPa, and the time is 10-30 min; the conditions for the second atomic deposition treatment can include: the temperature is 80-200 °C, the pressure is 1×10 -5 MPa, and the time is 10-30 min; the number of repetitions of step (1) and step (2) can be 5-20 times.

[0055] In an exemplary embodiment of the present invention, at the end of each atomic deposition treatment, it is necessary to reduce the pressure to remove the unreacted precursor, and then introduce an inert gas to clean the reaction chamber of the ALD device, and then carry out subsequent depositions after the reaction chamber of the ALD device is cleaned.

[0056] According to the present invention, the preparation method may further include: mixing a sodium source, a nickel source, an iron source, a manganese source, a zinc source, a calcium source, and a fluorine source to obtain a mixture powder; and calcining the mixture powder to obtain the layered oxide cathode material. In the present invention, the molar ratio of the sodium source, the nickel source, the iron source, the manganese source, the zinc source, the calcium source, and the fluorine source in the mixture may be (2-4):(2-3.3):(3-4):(0.3-1):(0-0.1):(0-4):(18-22).

[0057] In the preparation method of the layered oxide cathode material of the present invention, primary particles doped with cations and anions are prepared by solid-phase sintering, and the structural stability is greatly improved through the synergistic effect of cations and anions, inhibiting the dissolution of metal ions. The improvement in the stability of the layered oxide cathode material is much higher than that of single cation or anion doping.

[0058] Exemplarily, the sodium source may include at least one of sodium carbonate, sodium acetate, sodium nitrate, and sodium hydroxide.

[0059] Exemplarily, the nickel source may include at least one of nickel oxide, nickel acetate, nickel nitrate, and nickel hydroxide.

[0060] Exemplarily, the iron source may include at least one of iron(III) oxide, iron acetate, iron nitrate, and iron hydroxide.

[0061] Exemplarily, the manganese source may include at least one of manganese dioxide, manganese acetate, manganese nitrate, and manganese hydroxide.

[0062] Exemplarily, the zinc source may include at least one of zinc oxide, zinc acetate, zinc nitrate, and zinc hydroxide.

[0063] Exemplarily, the calcium source may include at least one of calcium oxide, calcium acetate, calcium nitrate, and calcium hydroxide.

[0064] Exemplarily, the fluorine source may include one of sodium fluoride and / or ammonium fluoride.

[0065] According to the present invention, the mixing treatment may be ball milling treatment, and the conditions of the ball milling treatment may include: a mixing temperature of 40-80°C, a mixing time of 4-10 h, and a mixing rotation speed of 200-600 rpm / min; the conditions of the calcining treatment may include: a calcining temperature of 600-1000°C and a calcining time of 360-600 min.

[0066] The third aspect of the present invention provides a battery, the battery includes a positive electrode sheet, the positive electrode sheet contains a positive electrode active material, wherein the positive electrode active material includes the above-mentioned positive electrode material and / or the positive electrode material prepared according to the above-mentioned preparation method.

[0067] The present invention will be further described in detail by way of examples. The raw materials used in the examples can all be obtained through commercial channels.

[0068] Example 1

[0069] (I) NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 Preparation of Sodium - Ion Battery Cathode Material

[0070] Sodium carbonate, nickel oxide, manganese dioxide, iron oxide, zinc oxide, calcium oxide and sodium fluoride were placed in a ball - milling jar according to a molar ratio of 0.50:0.32:0.15:0.33:0.04:0.01:0.40 and milled at 450 rpm / min for 6 h. The wet - milling aid was absolute ethanol. After milling, it was dried at 70 °C to obtain a mixture powder; the mixture powder was placed in a muffle furnace and calcined. The temperature was raised to 950 °C at a heating rate of 4 °C / min, held for 10 h and then naturally cooled to room temperature, and then sufficiently milled to obtain the target product NaNi 0.32 Fe 0. 3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 sodium - ion battery cathode material.

[0071] (II) Preparation of Sodium - Ion Battery Cathode Material Coated with Manganese Phosphate

[0072] The sodium - ion battery cathode material prepared in this example was placed in the reaction chamber of a dry atomic layer deposition (ALD) device. The temperature of the reaction chamber was raised to 180 °C and the temperature of the pipeline was 80 °C;

[0073] (1) After sealing the reaction chamber, the pressure was reduced to 1×10 -5 MPa, and ethylcyclopentadienylmanganese vapor was introduced into the reaction chamber, held for a certain time, and then the unreacted ethylcyclopentadienylmanganese was removed by reducing the pressure;

[0074] (2) Inert gas argon was introduced to clean the reaction chamber;

[0075] (3) After reducing the pressure again, trimethyl phosphate vapor was introduced into the reaction chamber. After reacting sufficiently for a certain time, the unreacted trimethyl phosphate was removed by reducing the pressure;

[0076] (4) Inert gas argon was introduced to further clean the reaction chamber;

[0077] (1) to (4) is a complete cycle process. The above cycle is repeated 20 times to obtain a 10 nm thick manganese phosphate coating layer, thereby obtaining the manganese phosphate-coated sodium positive electrode material of this embodiment; wherein the SEM image of the manganese phosphate-coated sodium positive electrode material of this embodiment is shown in FIG. Figure 1 .

[0078] (III) Preparation of button cells

[0079] The 10MP-NaNi prepared in this example 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 The material and the conductive agent Super P, the binder polyvinylidene fluoride (PVDF) are mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 8:1:1, and then coated with aluminum foil and dried in a blast drying oven at 80°C for 1h, and in a vacuum drying oven at 120°C for 12h; cut into 14mm round positive electrode sheets. A sodium metal sheet with a diameter of 14mm and a thickness of 0.15mm is used as the negative electrode, a 0.1mol / L sodium perchlorate / ethylene carbonate / dimethyl carbonate solution is used as the electrolyte, and a Whatman GF / F glass fiber with a diameter of 16mm is used as the diaphragm. The CR2025 button cell of this embodiment is assembled in a glove box filled with high-purity argon.

[0080] Example 2

[0081] (I) NaNi 0.31 Fe 0.3 Mn 0.33 Zn 0.05 Ca 0.01 O 1.8 F 0.4 Preparation of sodium battery cathode materials

[0082] Sodium carbonate, nickel oxide, manganese dioxide, iron oxide, zinc oxide, calcium oxide and sodium fluoride were placed in a ball mill at a molar ratio of 0.50:0.31:0.15:0.33:0.05:0.01:0.40 and ground at 450 rpm / min for 6 hours. The wet grinding aid was anhydrous ethanol. After grinding, the mixture was dried at 70°C to obtain a mixture powder. The mixture powder was calcined in a muffle furnace, heated to 950°C at a heating rate of 4°C / min, kept warm for 10 hours, and then naturally cooled to room temperature. The target product NaNi 0.31 Fe 0. 3 Mn 0.33 Zn 0.05 Ca 0.01 O 1.8 F 0.4Sodium-based cathode material.

[0083] In this example, the preparation method of the sodium-based cathode material coated with manganese phosphate and the preparation method of the button cell are the same as those in Example 1.

[0084] Example 3

[0085] (I) NaNi 0.3 Fe 0.3 Mn 0.33 Zn 0.06 Ca 0.01 O 1.8 F 0.4 Preparation of sodium-based cathode material

[0086] Sodium carbonate, nickel oxide, manganese dioxide, iron oxide, zinc oxide, calcium oxide and sodium fluoride were placed in a ball mill at a molar ratio of 0.50:0.30:0.15:0.33:0.06:0.01:0.40 and ground at 450 rpm for 6 h. The wet grinding aid was absolute ethanol. After grinding, the mixture was dried at 70 °C to obtain a mixture powder. The mixture powder was placed in a muffle furnace and calcined. The temperature was raised to 950 °C at a heating rate of 4 °C / min, held for 10 h, and then naturally cooled to room temperature. After thorough grinding, the target product NaNi 0.3 Fe 0.3 Mn 0.33 Zn 0.06 Ca 0.01 O 1.8 F 0.4 Sodium-based cathode material.

[0087] In this example, the preparation method of the sodium-based cathode material coated with manganese phosphate and the preparation method of the button cell are the same as those in Example 1.

[0088] Example 4

[0089] (I) NaNi 0.29 Fe 0.3 Mn 0.33 Zn 0.07 Ca 0.01 O 1.8 F 0.4 Preparation of sodium-based cathode material

[0090] Mix sodium carbonate, nickel oxide, manganese dioxide, iron oxide, zinc oxide, calcium oxide and sodium fluoride in a molar ratio of 0.50:0.29:0.15:0.33:0.07:0.01:0.40 and place them in a ball mill jar. Grind at 450 rpm for 6 hours. The wet grinding aid is anhydrous ethanol. After grinding, dry at 70 °C to obtain a mixture powder; place the mixture powder in a muffle furnace and calcine. Heat it to 950 °C at a heating rate of 4 °C / min, keep it at this temperature for 10 hours, and then cool it naturally to room temperature. Grind thoroughly to obtain the target product NaNi 0.29 Fe 0. 3 Mn 0.33 Zn 0.07 Ca 0.01 O 1.8 F 0.4 sodium-ion battery cathode material.

[0091] In this example, the preparation method of the sodium-ion battery cathode material coated with manganese phosphate and the preparation method of the button battery are the same as those in Example 1.

[0092] Example 5

[0093] (I) NaNi 0.28 Fe 0.3 Mn 0.33 Zn 0.08 Ca 0.01 O 1.8 F 0.4 Preparation of sodium-ion battery cathode material

[0094] Mix sodium carbonate, nickel oxide, manganese dioxide, iron oxide, zinc oxide, calcium oxide and sodium fluoride in a molar ratio of 0.50:0.28:0.15:0.33:0.08:0.01:0.40 and place them in a ball mill jar. Grind at 450 rpm for 6 hours. The wet grinding aid is anhydrous ethanol. After grinding, dry at 70 °C to obtain a mixture powder; place the mixture powder in a muffle furnace and calcine. Heat it to 950 °C at a heating rate of 4 °C / min, keep it at this temperature for 10 hours, and then cool it naturally to room temperature. Grind thoroughly to obtain the target product NaNi 0.28 Fe 0. 3 Mn 0.33 Zn 0.08 Ca 0.01 O 1.8 F 0.4 sodium-ion battery cathode material.

[0095] In this example, the preparation method of the sodium-ion battery cathode material coated with manganese phosphate and the preparation method of the button battery are the same as those in Example 1.

[0096] Example 6

[0097] (I) NaNi0.27 Fe 0.3 Mn 0.33 Zn 0.09 Ca 0.01 O 1.8 F 0.4 Preparation of sodium battery cathode materials

[0098] Sodium carbonate, nickel oxide, manganese dioxide, iron oxide, zinc oxide, calcium oxide and sodium fluoride were placed in a ball mill at a molar ratio of 0.50:0.27:0.15:0.33:0.09:0.01:0.40 and ground at 450 rpm / min for 6 hours. The wet grinding aid was anhydrous ethanol. After grinding, the mixture was dried at 70°C to obtain a mixture powder. The mixture powder was calcined in a muffle furnace, heated to 950°C at a heating rate of 4°C / min, kept warm for 10 hours, and then naturally cooled to room temperature. The target product NaNi 0.27 Fe 0. 3 Mn 0.33 Zn 0.09 Ca 0.01 O 1.8 F 0.4 Sodium battery cathode materials.

[0099] The preparation method of the manganese phosphate-coated sodium positive electrode material and the preparation method of the button battery in this embodiment are the same as those in Example 1.

[0100] Example 7

[0101] (I) NaNi 0.26 Fe 0.3 Mn 0.33 Zn 0.1 Ca 0.01 O 1.8 F 0.4 Preparation of sodium battery cathode materials

[0102] Sodium carbonate, nickel oxide, manganese dioxide, iron oxide, zinc oxide, calcium oxide and sodium fluoride were placed in a ball mill at a molar ratio of 0.50:0.26:0.15:0.33:0.10:0.01:0.40 and ground at 450 rpm / min for 6 hours. The wet grinding aid was anhydrous ethanol. After grinding, the mixture was dried at 70°C to obtain a mixture powder. The mixture powder was calcined in a muffle furnace, heated to 950°C at a heating rate of 4°C / min, kept warm for 10 hours, and then naturally cooled to room temperature. The target product NaNi 0.26 Fe 0. 3 Mn 0.33 Zn 0.1 Ca 0.01 O 1.8 F 0.4Sodium-based cathode material.

[0103] In this example, the preparation method of the sodium-based cathode material coated with manganese phosphate and the preparation method of the coin cell are the same as those in Example 1.

[0104] Example 8

[0105] (I) NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 Preparation of the sodium-based cathode material

[0106] In this example, the preparation method of NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 The preparation method of the sodium-based cathode material is the same as that in Example 1.

[0107] (II) Preparation of the sodium-based cathode material coated with manganese phosphate

[0108] Put the sodium-based cathode material prepared in this example into the reaction chamber of a dry atomic layer deposition (ALD) device, raise the temperature of the reaction chamber to 180 °C, and the temperature of the pipeline to 80 °C;

[0109] (1) After sealing the reaction chamber, reduce the pressure to 1×10 -5 MPa, introduce ethylcyclopentadienyl manganese vapor into the reaction chamber, keep it for a certain time, and then reduce the pressure to remove the unreacted ethylcyclopentadienyl manganese;

[0110] (2) Introduce the inert gas argon to clean the reaction chamber;

[0111] (3) After reducing the pressure again, introduce trimethyl phosphate vapor into the reaction chamber, keep it for a certain time for sufficient reaction, and then reduce the pressure to remove the unreacted trimethyl phosphate;

[0112] (4) Introduce the inert gas argon to further clean the reaction chamber;

[0113] (1) to (4) is a complete cycle process. Repeat the above cycle 10 times to obtain a 5-nm-thick manganese phosphate coating, and obtain the sodium-based cathode material coated with manganese phosphate in this example.

[0114] (III) Preparation of the coin cell

[0115] In this example, the preparation method of the sodium-based cathode material coated with manganese phosphate and the preparation method of the coin cell are the same as those in Example 1.

[0116] Example 9

[0117] (I) NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 Preparation of Sodium - Ion Battery Cathode Material

[0118] In this example, NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 The preparation method of the sodium - ion battery cathode material is the same as that in Example 1.

[0119] (II) Preparation of Manganese Phosphate - Coated Sodium - Ion Battery Cathode Material

[0120] Put the sodium - ion battery cathode material prepared in this example into the reaction chamber of a dry atomic layer deposition (ALD) device, raise the temperature of the reaction chamber to 180 °C, and the temperature of the pipeline to 80 °C;

[0121] (1) After sealing the reaction chamber, reduce the pressure to 1×10 -5 MPa, introduce ethylcyclopentadienylmanganese vapor into the reaction chamber, keep it for a certain time, and then reduce the pressure to remove the unreacted ethylcyclopentadienylmanganese;

[0122] (2) Pass in the inert gas argon to clean the reaction chamber;

[0123] (3) After reducing the pressure again, introduce trimethyl phosphate vapor into the reaction chamber, keep it for a certain time for sufficient reaction, and then reduce the pressure to remove the unreacted trimethyl phosphate;

[0124] (4) Pass in the inert gas argon to further clean the reaction chamber;

[0125] (1) - (4) is a complete cycle process. Repeat the above cycle 30 times to obtain a 15 - nm - thick manganese phosphate coating, and obtain the manganese phosphate - coated sodium - ion battery cathode material of this example.

[0126] (III) Preparation of Button Battery

[0127] In this example, the preparation method of the manganese phosphate - coated sodium - ion battery cathode material and the preparation method of the button battery are the same as those in Example 1.

[0128] Comparative Example 1

[0129] (I) NaNi 0.36 Fe 0.3 Mn 0.33 Ca0.01 O 1.8 F 0.4 Preparation of Sodium-ion Battery Cathode Material

[0130] Put sodium carbonate, nickel oxide, manganese dioxide, iron oxide, calcium oxide and sodium fluoride in a ball mill tank according to the molar ratio of 0.50:0.36:0.15:0.33:0.01:0.40 and grind at 450 rpm for 6 h. The wet grinding aid is anhydrous ethanol. After grinding, dry at 70 °C to obtain a mixture powder; put the mixture powder in a muffle furnace for calcination, heat up to 950 °C at a heating rate of 4 °C / min, keep warm for 10 h, then cool naturally to room temperature, and grind thoroughly to obtain the target product NaNi 0.36 Fe 0.3 Mn 0.33 Ca 0.01 O 1. 8 F 0.4 sodium-ion battery cathode material.

[0131] (II) Preparation of Sodium-ion Battery Cathode Material Coated with Manganese Phosphate

[0132] Put the sodium-ion battery cathode material prepared in this comparative example into the reaction chamber of a dry atomic layer deposition (ALD) device, raise the temperature of the reaction chamber to 180 °C, and the temperature of the pipeline to 80 °C;

[0133] (1) After closing the reaction chamber, reduce the pressure to 1×10 -5 MPa, introduce ethylcyclopentadienylmanganese vapor into the reaction chamber, keep it for a certain time, and then reduce the pressure to remove the unreacted ethylcyclopentadienylmanganese;

[0134] (2) Introduce inert gas argon to clean the reaction chamber;

[0135] (3) After reducing the pressure again, introduce trimethyl phosphate vapor into the reaction chamber, keep it for a certain time for sufficient reaction, and then reduce the pressure to remove the unreacted trimethyl phosphate before;

[0136] (4) Introduce inert gas argon to further clean the reaction chamber;

[0137] (1) to (4) is a complete cycle process. Repeat the above cycle 20 times to obtain a 10-nm-thick manganese phosphate coating, and obtain the manganese phosphate-coated sodium-ion battery cathode material of this comparative example.

[0138] (III) Preparation of Coin Cell

[0139] The preparation method of the manganese phosphate-coated sodium-ion battery cathode material and the preparation method of the coin cell in this comparative example are the same as those in Example 1.

[0140] Comparative Example 2

[0141] (I) NaNi0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 Preparation of the cathode material for sodium battery.

[0142] In this comparative example, NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 The preparation method of the cathode material for sodium battery is the same as that in Example 1.

[0143] (III) Preparation of coin cells

[0144] The prepared NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 The material, conductive agent Super P, and binder PVDF were added in a mass ratio of 8:1:1, mixed evenly with an appropriate amount of NMP, coated on aluminum foil, dried at 80 °C for 1 h in a forced-air drying oven, and dried at 120 °C for 12 h in a vacuum drying oven; then cut into 14-mm circular positive electrode sheets. A sodium metal sheet with a diameter of 14 mm and a thickness of 0.15 mm was used as the negative electrode, a 0.1 mol / L sodium perchlorate / ethylene carbonate / dimethyl carbonate solution was used as the electrolyte, and a Whatman GF / F glass fiber with a diameter of 16 mm was used as the separator. A CR2025 coin cell was assembled in a glove box filled with high-purity argon.

[0145] Table 1 shows the components of the positive electrode materials prepared in each example and comparative example.

[0146] Table 1

[0147] Group Component Example 1 <![CDATA[10MP-NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 > Example 2 <![CDATA[10MP-NaNi 0.31 Fe 0.3 Mn 0.33 Zn 0.05 Ca 0.01 O 1.8 F 0.4 > Example 3 <![CDATA[10MP-NaNi 0.3 Fe 0.3 Mn 0.33 Zn 0.06 Ca 0.01 O 1.8 F 0.4 > Example 4 <![CDATA[10MP-NaNi 0.29 Fe 0.3 Mn 0.33 Zn 0.07 Ca 0.01 O 1.8 F 0.4 > Example 5 <![CDATA[10MP-NaNi 0.28 Fe 0.3 Mn 0.33 Zn 0.08 Ca 0.01 O 1.8 F 0.4 > Example 6 <![CDATA[10MP-NaNi 0.27 Fe 0.3 Mn 0.33 Zn 0.09 Ca 0.01 O 1.8 F 0.4 > Example 7 <![CDATA[10MP-NaNi 0.26 Fe 0.3 Mn 0.33 Zn 0.1 Ca 0.01 O 1.8 F 0.4 > Example 8 <![CDATA[5MP-NaNi 0.33 Fe 0.3 Mn 0.33 Zn 0.03 Ca 0.01 O 1.8 F 0.4 > Example 9 <![CDATA[15MP-NaNi 0.34 Fe 0.3 Mn 0.33 Zn 0.02 Ca 0.01 O 1.8 F 0.4 > Comparative Example 1 <![CDATA[NaNi 0.36 Fe 0.3 Mn 0.33 Ca 0.01 O 1.8 F 0.4 > Comparative Example 2 <![CDATA[NaNi 0.32 Fe 0.3 Mn 0.33 Zn 0.04 Ca 0.01 O 1.8 F 0.4 >

[0148] Test Example 1

[0149] The coin cells prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to coin cell discharge testing and cycling performance testing. The test results are shown in Table 2.

[0150] Coin cell discharge testing: The test conditions were LR 2032, 0.1C, 2.5-4.0 V, and the charge-discharge equipment used was a BlueTEC charge-discharge instrument.

[0151] Cycling performance test: The lithium-ion battery is left standing at 25°C for 30 min, charged at a constant current of 1C to 4.4V, then charged at a constant voltage of 4.4V until the current reaches 0.05C, and then discharged at a constant current of 1C to 2.8V. Record the discharge capacity at this time and the discharge capacity of the first cycle. Leave it standing for 10 min and record the capacity of the lithium-ion battery when cycling to the 500th cycle; The capacity retention rate of the 500th cycle = the discharge capacity of the 500th cycle / the discharge capacity of the first cycle.

[0152] Perform SEM testing on the sodium-ion battery cathode material coated with manganese phosphate prepared in Example 1. The specific testing method is to first stick the conductive tape on the sample stage, then evenly sprinkle the powder sample on the conductive tape, and then blow off the unadhered sample with compressed air (or an ear bulb), which can well prevent the unadhered sample from contaminating the equipment, and then place it in the scanning electron microscope for observation. The obtained SEM image is shown in Figure 1 .

[0153] Table 2

[0154] Group Initial discharge capacity of 1C (mAh / g) Capacity retention rate after 500 cycles (%) Example 1 133.2 91.1 Example 2 130.3 87.2 Example 3 130.4 84.6 Example 4 129.4 82.4 Example 5 129.1 80.2 Example 6 129.5 79.2 Example 7 129.9 76.5 Example 8 130.2 88.2 Example 9 129.2 89.3 Comparative Example 1 128.6 87.8 Comparative Example 2 130.8 80.5

[0155] It can be seen from the data in Table 2 that the cathode material of the present invention has a significantly improved initial discharge capacity at 1C and a capacity retention rate of 500 cycles. Comparing Example 1 and Comparative Example 1, when the inner-layer layered oxide cathode material does not contain zinc element, the initial discharge capacity at 1C and the capacity retention rate of 500 cycles are significantly reduced; comparing Example 1 and Comparative Example 2, in Comparative Example 2, the layered oxide cathode material is not coated, and the capacity retention rate of 500 cycles is significantly reduced. It can be seen from the comparison of Example 1, Example 8 and Example 9 that by adjusting the thickness of the inner-layer layered oxide cathode material and the outer-layer phosphate coating layer, the initial discharge capacity at 1C and the capacity retention rate of 500 cycles can be significantly affected. It can be seen that through the synergistic effect of element doping and phosphate coating in the examples of the present invention, the cycling stability of the zinc-based sodium-ion battery cathode material is greatly improved.

[0156] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that: The positive electrode material comprises a layered oxide positive electrode material and a coating layer coated on the surface of the layered oxide positive electrode material; The material of the coating layer includes phosphate; Wherein, the layered oxide positive electrode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x+y+z+p+q=1, 0.2≤x≤0.4, 0.2≤y≤0.33, 0.3≤z≤0.4, 0.03≤p≤0.1, 0<q≤0.01, 0<n≤0.4, 1.8≤m≤2.2, 0.8≤w≤1.

2.

2. The positive electrode material according to claim 1, characterized in that The layered oxide positive electrode material comprises a P2-type layered oxide positive electrode material, wherein the P2-type layered oxide positive electrode material comprises Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x+y+z+p+q=1, 0.2≤x≤0.4, 0.2≤y≤0.33, 0.3≤z≤0.4, 0.03≤p≤0.1, 0<q≤0.01, 0<n≤0.4, 1.8≤m≤2.2, 0.8≤w≤1.0; or, The layered oxide positive electrode material comprises an O3-type layered oxide positive electrode material, wherein the O3-type layered oxide positive electrode material comprises Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x+y+z+p+q=1, 0.2≤x≤0.4, 0.2≤y≤0.33, 0.3≤z≤0.4, 0.03≤p≤0.1, 0<q≤0.01, 0<n≤0.4, 1.8≤m≤2.2, 1.0<w≤1.2; The phosphate includes manganese phosphate and / or sodium manganese phosphate.

3. The positive electrode material according to claim 1, characterized in that The D50 of the layered oxide positive electrode material is 6.0 to 9.0 μm, preferably 7.2 to 7.8 μm; Based on the total mass of the positive electrode material, the content of the layered oxide positive electrode material is 95 to 99.9 wt %, preferably 99 to 99.5 wt %.

4. The positive electrode material according to claim 1, characterized in that The coating layer has a thickness of 5 to 20 nm, preferably 8 to 12 nm.

5. A method for preparing a positive electrode material, characterized in that: The preparation method comprises the following steps: (1) mixing a layered oxide positive electrode material with a first precursor and performing a first atomic deposition process to obtain a first material; (2) mixing the first material with a second precursor and performing a second atomic deposition process to obtain a second material; (3) Repeat steps (1) and (2) 5 to 60 times; Wherein, the layered oxide positive electrode material includes Na w Ni x Fe y Mn z Zn p Ca q O m F n , where x+y+z+p+q=1, 0.2≤x≤0.4, 0.2≤y≤0.33, 0.3≤z≤0.4, 0.03≤p≤0.1, 0<q≤0.01, 0<n≤0.4, 1.8≤m≤2.2, 0.8<w<1.2; The first precursor includes ethyl manganocene; and the second precursor includes trimethyl phosphate.

6. The preparation method according to claim 5, characterized in that: The mass ratio of the layered oxide positive electrode material to the first precursor is 1:0.0001-0.01; the mass ratio of the first material to the second precursor is 1:0.3-0.6; The conditions of the first atomic deposition process include: a temperature of 80 to 200° C., a pressure of 1×10 -5 MPa, time is 10 to 30 minutes; The conditions of the second atomic deposition process include: a temperature of 80 to 200° C., a pressure of 1×10 -5 MPa, time is 10 to 30 minutes; The steps (1) and (2) are repeated 5 to 20 times.

7. The preparation method according to claim 5, characterized in that: The preparation method further comprises: Mixing a sodium source, a nickel source, an iron source, a manganese source, a zinc source, a calcium source and a fluorine source to obtain a mixture powder; calcining the mixture powder to obtain the layered oxide positive electrode material; Optionally, the molar ratio of the sodium source, the nickel source, the iron source, the manganese source, the zinc source, the calcium source and the fluorine source is (2-4): (2-3.3): (3-4): (0.3-1): (0-0.1): (0-4): (18-22).

8. The preparation method according to claim 7, characterized in that: The sodium source includes at least one of sodium carbonate, sodium acetate, sodium nitrate and sodium hydroxide; The nickel source includes at least one of nickel oxide, nickel acetate, nickel nitrate and nickel hydroxide; The iron source includes at least one of ferric oxide, ferric acetate, ferric nitrate and ferric hydroxide; The manganese source includes at least one of manganese dioxide, manganese acetate, manganese nitrate and manganese hydroxide; The zinc source includes at least one of zinc oxide, zinc acetate, zinc nitrate and zinc hydroxide; The calcium source includes at least one of calcium oxide, calcium acetate, calcium nitrate and calcium hydroxide; The fluoride source includes one of sodium fluoride and / or ammonium fluoride.

9. The preparation method according to claim 7, characterized in that: The mixing process is a ball milling process, and the conditions of the ball milling process include: a mixing temperature of 40 to 80° C., a mixing time of 4 to 10 hours, and a mixing speed of 200 to 600 rpm / min; The calcination treatment conditions include: a calcination temperature of 600 to 1000° C. and a calcination time of 360 to 600 minutes.

10. A battery, characterized in that: The battery comprises a positive electrode sheet, and the positive electrode sheet contains a positive electrode active material, wherein the positive electrode active material comprises the positive electrode material according to any one of claims 1 to 4 and / or the positive electrode material prepared according to the preparation method according to any one of claims 5 to 9.

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