Positive electrode material and preparation method and application thereof

Abstract

In order to solve the problem that an existing positive electrode material is poor in rate capability and cycle performance, the invention provides a positive electrode material and a preparation method and application thereof, the general formula of the positive electrode material is [NaxAy] [NiaFebMncCudTieMzXw] O2, 0.6 < = x < = 1, 0 < = y < = 0.1, 0.05 < = a < = 0.4, 0.05 < = b < = 0.6, 0.1 < = c < = 0.7, 0.01 < = d < = 0.25, 0.01 < = e < = 0.2, 0.01 < z < 0.15, 0.01 < w < 0.1, and a + b + c + d + e + z + w = 1, A is selected from at least one of lithium and potassium, M is an element with the ion radius of 40-70 pm, and 0 < = x < = 0.5. And X is an element with an ion radius greater than or equal to 70 pm. The positive electrode material has relatively high capacity, good rate capability and cycle performance through metal doping design and regulation and control of sodium content and occupation.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium-ion batteries, and particularly relates to a cathode material, a preparation method thereof, and an application thereof. Background Art

[0003] Sodium-ion batteries are a kind of clean, efficient, and renewable secondary ion batteries. The abundant sodium resources in the earth's crust make them become inexpensive energy storage devices to solve current energy crises and environmental pollution problems. The cathode material in sodium-ion batteries is one of its most important components, which determines the stability and charge-discharge performance of the battery. Layered oxides are the most common materials in cathode materials. Compared with polyanion-type and Prussian blue-type materials, their synthesis cost and industrialization difficulty are lower. However, during the process of sodium ion extraction and insertion in this type of material, multiple phase transitions occur, resulting in large volume changes and severe capacity attenuation, leading to poor cycle stability.

[0004] Therefore, there is an urgent need to develop a cathode material with high capacity, good cycle and rate performance. Summary of the Invention

[0005] Aiming at the problems of poor rate performance and cycle performance of existing cathode materials, the present invention provides a cathode material, a preparation method thereof, and an application thereof.

[0006] The technical solutions adopted by the present invention to solve the above technical problems are as follows: In the first aspect, the present invention provides a cathode material, and the general formula of the cathode material is: [Na x A y [Ni a Fe b Mn c Cu d Ti e M z X w O 2 , where 0.6≤x≤1, 0≤y≤0.1, 0.05≤a≤0.4, 0.05≤b≤0.6, 0.1≤c≤0.7, 0.01≤d≤0.25, 0.01≤e≤0.2, 0.01<z<0.15, 0.01<w<0.1, a + b + c + d + e + z + w = 1, A is selected from at least one of lithium and potassium, M is an element with an ionic radius of 40 - 70 pm, and X is an element with an ionic radius greater than or equal to 70 pm.

[0007] Optionally, 0.85≤a + b + c + d + e≤0.95.

[0008] Optionally, the M is selected from at least two of aluminum, vanadium, chromium, molybdenum, and cobalt. Optionally, X is selected from at least three of magnesium, tin, zinc, gallium, germanium, niobium, zirconium, yttrium, antimony, and calcium.

[0009] Optionally, the general formula of the positive electrode material is: [Na x A y [Ni a Fe b Mn c Cu d Ti e Co f Al g Mg h Zn i Sn j O 2 , where 0.6 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, 0.05 ≤ a ≤ 0.4, 0.05 ≤ b ≤ 0.6, 0.1 ≤ c ≤ 0.7, 0.01 ≤ d ≤ 0.25, 0.01 ≤ e ≤ 0.2, 0.01 ≤ f < 0.15, 0.01 ≤ g < 0.1, 0.01 ≤ h < 0.1, 0.01 ≤ i < 0.1, 0.01 ≤ j < 0.1, and A is selected from at least one of lithium and potassium. In a second aspect, the present invention also provides a method for preparing a positive electrode material as described in any one of the above, comprising the following steps: According to [Na x A y [Ni a Fe b Mn c Cu d Ti e M z X w O 2 , where 0.6 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, 0.05 ≤ a ≤ 0.4, 0.05 ≤ b ≤ 0.6, 0.1 ≤ c ≤ 0.7, 0.01 ≤ d ≤ 0.25, 0.01 ≤ e ≤ 0.2, 0.01 < z < 0.15, 0.01 < w < 0.1, the sodium source, lithium source, potassium source, nickel source, iron source, manganese source, copper source, titanium source, the compound containing element M, and the compound containing element X are added to a solvent and stirred to obtain a metal salt solution that is uniformly mixed at the ionic scale; The metal salt solution is dropped into a solution containing a chelating agent, continuously stirred and the solvent is evaporated, and then dried to obtain a positive electrode precursor material; The positive electrode precursor material is heat-treated and cooled to obtain a positive electrode material.

[0010] Optionally, the heat treatment includes the following steps: The positive electrode precursor material is subjected to preliminary sintering, heated at a heating rate of 3 - 5 °C / min to 480 - 550 °C for sintering, and the sintering time is 6h - 8h; After cooling the preliminarily sintered positive electrode precursor material, it is coarsely ground to obtain solid powder; The solid powder is subjected to final sintering, heated at a heating rate of 3 - 5 °C / min to 850 - 1000 °C for sintering, and the sintering time is 12h - 20h. After final sintering of the solid powder, it is cooled to obtain the positive electrode material. Optionally, the sodium source includes at least one of sodium carbonate, sodium citrate, and sodium oxalate; The lithium source includes at least one of lithium acetate, lithium oxalate, and lithium carbonate; The potassium source includes at least one of potassium acetate, potassium oxalate, and potassium carbonate; The nickel source includes at least one of nickel acetate and nickel oxalate; The iron source includes at least one of iron acetate, iron oxalate, and iron nitrate; The manganese source includes at least one of manganese acetate, manganese oxalate, and manganese dioxide; The copper source includes at least one of copper acetate, copper oxalate, and copper oxide; The titanium source includes at least one of titanium acetate, titanium oxalate, and titanate; And / or, the chelating agent includes at least one of ethylenediaminetetraacetic acid, citric acid, glycolic acid, and acrylic acid. In a third aspect, the present invention provides a positive electrode sheet, including a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector. The positive electrode active material layer includes the positive electrode material as described in any one of the above, or the positive electrode active material layer includes the positive electrode material prepared by the preparation method described in any one of the above.

[0011] In a fourth aspect, the present invention provides a battery, including the positive electrode sheet as described in any one of the above.

[0012] In the present invention, in the first aspect, by regulating the ratio of each element and the sodium ion occupancy, the specific capacity of the cathode material is increased, and at the same time, the rate performance is improved. By doping a variety of elements in the transition metal layer of the cathode material, the synergistic effect of multiple elements and the high-entropy effect are utilized to effectively enhance the TM-O bond, effectively enhance the structural stability of the cathode material, and at the same time expand the transition metal layer, so that the sodium ion transport channel is expanded, further improving the rate performance of the material. Doping lithium and / or potassium in the alkali metal layer, lithium ions and / or potassium ions migrate reversibly in the transition metal layer and the sodium layer. Therefore, a solid solution reaction occurs in the cathode material during the charge and discharge process. Among them, lithium ions and / or potassium ions play a supporting role during deep sodiation, improving the structural stability of the cathode material at high voltages and ensuring the cycle performance of the battery. By limiting the ionic radii of the doped elements M and A, on the one hand, the sodium ion transport channel is optimized to facilitate the insertion and extraction of sodium ions. On the other hand, by limiting the ionic radii of M and A, it is convenient for M and A to form stable chemical bonds and coordination structures with surrounding ions, enhancing the stability of the crystal structure of the cathode material.

[0013] In the second aspect, the present invention first complexes a metal salt solution with a chelating agent and evaporates the solvent to form a gel-like cathode precursor, and then heat-treats the cathode precursor. Compared with the solid-phase method and the co-precipitation method, the preparation method of the present invention makes the obtained cathode material have a more uniform element distribution and a more stable structure. Compared with the traditional molten salt method, the raw materials in the preparation method of the present invention are cheap, green, environmentally friendly and pollution-free, and the preparation process is simple, suitable for commercial production. Detailed implementation manners

[0014] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0015] An embodiment of the present invention provides a cathode material, and the general formula of the cathode material is: [Na x A y [Ni a Fe b Mn c Cu d Ti e M z X w O 2, where 0.6 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, 0.05 ≤ a ≤ 0.4, 0.05 ≤ b ≤ 0.6, 0.1 ≤ c ≤ 0.7, 0.01 ≤ d ≤ 0.25, 0.01 ≤ e ≤ 0.2, 0.01 < z < 0.15, 0.01 < w < 0.1, a + b + c + d + e + z + w = 1, A is selected from at least one of lithium and potassium, M is an element with an ionic radius of 40 - 70 pm, and X is an element with an ionic radius greater than or equal to 70 pm.

[0016] In this embodiment, by regulating the ratio of each element and the sodium ion occupancy, the specific capacity of the cathode material is increased, and at the same time, the rate performance is improved. By doping multiple elements in the transition metal layer of the cathode material, the synergistic effect and high-entropy effect of multiple elements are utilized to effectively enhance the TM - O bond, effectively enhance the structural stability of the cathode material, and at the same time expand the transition metal layer, so that the sodium ion transport channel is expanded, further improving the rate performance of the material. Doping lithium and / or potassium in the alkali metal layer, lithium ions and / or potassium ions migrate reversibly between the transition metal layer and the sodium layer. Therefore, a solid solution reaction occurs in the cathode material during charge and discharge. Among them, lithium ions and / or potassium ions play a supporting role during deep sodiation, improving the structural stability of the cathode material at high voltages and ensuring the cycle performance of the battery. By limiting the ionic radii of the doped elements M and A, on the one hand, the sodium ion transport channel is optimized to facilitate the insertion and extraction of sodium ions. On the other hand, by limiting the ionic radii of M and A, it is convenient for M and A to form stable chemical bonds and coordination structures with surrounding ions, enhancing the stability of the crystal structure of the cathode material. Furthermore, the cathode material has a layered structure and a specific capacity of not less than 170 mAh / g.

[0017] In one embodiment, 0.85 ≤ a + b + c + d + e ≤ 0.95. By limiting the range of a + b + c + d + e, the content of the doped elements is limited, so that a synergistic effect and high-entropy effect are generated among the doped elements, effectively enhancing the TM - O bond, enhancing the structural stability of the cathode material and ensuring good capacity.

[0018] In one embodiment, M is selected from at least two of aluminum, vanadium, chromium, molybdenum, and cobalt. By limiting M to be selected from the above elements, the crystal structure of the cathode material is improved, the ion diffusion coefficient, conductivity, rate performance are increased, and the stability of the lattice oxygen of the cathode material is enhanced. In one embodiment, X is selected from at least three of magnesium, tin, zinc, gallium, germanium, niobium, zirconium, yttrium, antimony, and calcium. By defining that X is selected from the above elements, the crystal structure and cycle stability of the cathode material are improved. Through the doping of the above elements, it is beneficial to inhibit the phase change of the cathode material, and through the synergistic doping modification of multiple elements, the structural stability of the cathode material can be improved, and the distortion and collapse of the crystal structure during charge and discharge can be reduced, thereby extending the cycle life of the battery.

[0019] In one embodiment, the general formula of the cathode material is: [Na x A y [Ni a Fe b Mn c Cu d Ti e Co f Al g Mg h Zn i Sn j O 2 , where 0.6 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, 0.05 ≤ a ≤ 0.4, 0.05 ≤ b ≤ 0.6, 0.1 ≤ c ≤ 0.7, 0.01 ≤ d ≤ 0.25, 0.01 ≤ e ≤ 0.2, 0.01 ≤ f < 0.15, 0.01 ≤ g < 0.1, 0.01 ≤ h < 0.1, 0.01 ≤ i < 0.1, 0.01 ≤ j < 0.1, and A is selected from at least one of lithium and potassium. Through the synergistic effect of the above doping elements, the structure of the cathode material has better stability, and the rate performance, conductivity, and cycle stability of the cathode material are improved.

[0020] An embodiment of the present invention also provides a preparation method of the cathode material as described in any one of the above, including the following steps: According to the ratio of [Na x A y [Ni a Fe b Mn c Cu d Ti e M z X w O 2 , where 0.6 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, 0.05 ≤ a ≤ 0.4, 0.05 ≤ b ≤ 0.6, 0.1 ≤ c ≤ 0.7, 0.01 ≤ d ≤ 0.25, 0.01 ≤ e ≤ 0.2, 0.01 < z < 0.15, 0.01 < w < 0.1, add sodium source, lithium source, potassium source, nickel source, iron source, manganese source, copper source, titanium source, compound containing M element and compound containing X element into the solvent and stir to obtain a metal salt solution that is uniformly mixed at the ionic scale; specifically, the solvent is water.

[0021] Drop the metal salt solution into the solution containing the chelating agent, continuously stir and evaporate the solvent to dryness, and then dry to obtain the cathode precursor material; Heat-treat the cathode precursor material and cool to obtain the cathode material.

[0022] In this embodiment, by first complexing the metal salt solution with the chelating agent and evaporating the solvent to form a gel-like cathode precursor, and then heat-treating the cathode precursor, compared with the solid-phase method and the co-precipitation method, the preparation method of the present invention makes the element distribution of the obtained cathode material more uniform and the structure more stable. Compared with the traditional molten salt method, the raw materials in the preparation method of the present invention are cheap, green and environmentally friendly, and the preparation process is simple, suitable for commercial production.

[0023] In one embodiment, the heat treatment includes the following steps: Pre-sinter the cathode precursor material, raise the temperature to 480-550 °C at a heating rate of 3-5 °C / min for sintering, and the sintering time is 6h-8h; Cool the pre-sintered cathode precursor material and then coarsely grind it to obtain solid powder; Final-sinter the solid powder, raise the temperature to 850-1000 °C at a heating rate of 3-5 °C / min for sintering, and the sintering time is 12h-20h. Cool the solid powder after final-sintering to obtain the cathode material. Through staged sintering, it is beneficial to the structural stability of the cathode material.

[0024] Specifically, the method of coarse grinding can include but is not limited to grinding with an agate mortar, ball milling with an agate ball milling jar, planetary ball milling, air flow pulverization, etc. In one embodiment, the sodium source includes at least one of sodium carbonate, sodium citrate, and sodium oxalate; The lithium source includes at least one of lithium acetate, lithium oxalate, and lithium carbonate; The potassium source includes at least one of potassium acetate, potassium oxalate, and potassium carbonate; The nickel source includes at least one of nickel acetate and nickel oxalate; The iron source includes at least one of iron acetate, iron oxalate, and iron nitrate; The manganese source includes at least one of manganese acetate, manganese oxalate, and manganese dioxide; The copper source includes at least one of copper acetate, copper oxalate, and copper oxide; The titanium source includes at least one of titanium acetate, titanium oxalate, and titanate; By selecting the above raw materials, the preparation cost of the cathode material is reduced, and it is ensured that the preparation process is green and environmentally friendly.

[0025] In one embodiment, the chelating agent includes at least one of ethylenediaminetetraacetic acid, citric acid, glycolic acid, and acrylic acid. By using the chelating agent to turn the metal salt solution into a sol and forming a gel after drying, the elements in the cathode precursor material are evenly distributed.

[0026] Furthermore, evaporating the solvent includes methods such as water bath heating and direct heating, and the heating temperature is 60 - 110 °C. Drying can be carried out in a vacuum or non-vacuum constant temperature environment, with a temperature of 40 - 90 °C. The drying time is 10 - 24 h.

[0027] An embodiment of the present invention provides a cathode sheet, which includes a cathode current collector and a cathode active material layer disposed on at least one side of the cathode current collector. The cathode active material layer includes the cathode material described in any one of the above, or the cathode active material layer includes the cathode material prepared by the preparation method described in any one of the above.

[0028] An embodiment of the present invention provides a battery, which includes the cathode sheet described in any one of the above.

[0029] It should be noted here that although the cathode material of a sodium-ion battery is used as an example in the embodiments of the present invention, due to the similar properties of lithium, sodium, and potassium, the cathode materials of lithium-ion batteries and potassium-ion batteries invented with reference to the idea of the present invention should all be included in the protection scope of the present invention.

[0030] The present invention is further illustrated by the following examples.

[0031] Example 1 This example is used to illustrate the cathode material and its preparation method disclosed by the present invention. The preparation of the cathode material includes the following operating steps: The chemical formula of the prepared cathode material is: [Na 0.83 Li 0.02 [Ni 0.15 Fe 0.25 Mn 0.53 Cu 0.01 Ti 0.01 Co 0.01 Al 0.01 Mg 0.01 Zn 0.01 Sn 0.01 O 2 。

[0032] Weigh lithium acetate, sodium oxalate, nickel acetate, iron nitrate, manganese acetate, copper nitrate, cobalt acetate, magnesium acetate, aluminum nitrate, zinc acetate, tin acetate, and tetrabutyl titanate according to the atomic ratio of each element in the above chemical formula, and then add deionized water and stir well to form a metal salt solution that no longer changes color.

[0033] Dissolve citric acid in deionized water to prepare a chelating agent, and slowly drip the metal salt solution into the chelating agent solution and stir well. Heat it in a water bath at 80 °C to evaporate the water. The rotation speed of magnetic stirring is 500 rpm. Put the dried solid into a forced-air drying oven and dry it at a constant temperature of 60 °C for 15 h to obtain the cathode precursor material.

[0034] Sinter the cathode precursor material in a sintering furnace under an oxygen atmosphere at 500 °C for 6 h, and the heating rate is 4 °C / min. The powder obtained after air cooling is coarsely ground with an agate mortar for 5 min, and then final sintering is carried out. The final sintering temperature is 950 °C, the sintering time is 15 h, and the heating rate is 5 °C / min. The powder material after furnace cooling to 25 °C is quickly stored in an argon atmosphere to obtain the cathode material to be prepared.

[0035] Example 2 This example is used to illustrate the cathode material and its preparation method disclosed by the present invention. The preparation of the cathode material includes the following operating steps: The chemical formula of the prepared cathode material is: [Na 0.8 Li 0.05 K 0.05 [Ni 0.05 Fe 0.05 Mn 0.7 Cu 0.05 Ti 0.03 Co 0.03 Al 0.03 Mg 0.03 Zn 0.02 Sn 0.01 O 2 Weigh lithium acetate, potassium acetate, sodium oxalate, nickel acetate, iron nitrate, manganese acetate, copper nitrate, cobalt acetate, magnesium acetate, aluminum nitrate, zinc acetate, tin acetate and tetrabutyl titanate according to the atomic ratio of each element in the above chemical formula, add deionized water, and stir magnetically to fully form a metal salt solution that no longer changes color.

[0036] Dissolve citric acid in deionized water to prepare a chelating agent, and slowly drip the metal salt into the chelating agent solution and stir well. Heat it in a water bath at 60 °C to evaporate the water. The rotation speed of magnetic stirring is 900 rpm. Put the dried solid into a vacuum drying oven and dry it at a constant temperature of 90 °C for 10 h to obtain the cathode precursor material.

[0037] The positive electrode precursor material is sintered in a sintering furnace under an oxygen atmosphere at 480 °C for 8 h, with a heating rate of 3 °C / min. The powder obtained after air cooling is coarsely ground in an agate mortar for 5 min and then subjected to final sintering. The final sintering temperature is 1000 °C, the sintering time is 12 h, and the heating rate is 3 °C / min. The powder material after furnace cooling to 25 °C is quickly stored in an argon atmosphere to obtain the positive electrode material to be prepared.

[0038] Example 3 This example is used to illustrate the positive electrode material and its preparation method disclosed in the present invention. The preparation of the positive electrode material includes the following operating steps: The chemical formula of the prepared positive electrode material is: Na[Ni 0.05 Fe 0.6 Mn 0.1 Cu 0.05 Ti 0.05 Co 0.05 Al 0.02 Mg 0.03 Zn 0.03 Sn 0.02 O 2 Weigh sodium oxalate, nickel acetate, iron nitrate, manganese acetate, copper nitrate, cobalt acetate, magnesium acetate, aluminum nitrate, zinc acetate, tin acetate and tetrabutyl titanate according to the atomic ratio of each element in the above chemical formula, add deionized water, and stir magnetically until a metal salt solution that no longer changes color is formed.

[0039] Dissolve citric acid in deionized water to prepare a chelating agent, slowly drop the metal salt into the chelating agent solution and stir evenly. Heat in a water bath at 110 °C to evaporate the water. The rotation speed of magnetic stirring is 600 rpm. Put the solid after evaporation into a blast drying oven and dry at 80 °C for 12 h to obtain the positive electrode precursor material.

[0040] The positive electrode precursor material is sintered in a sintering furnace under an oxygen atmosphere at 550 °C for 7 h, with a heating rate of 5 °C / min. The powder obtained after air cooling is ball milled in a planetary ball mill for 15 min and then subjected to final sintering. The final sintering temperature is 850 °C, the sintering time is 20 h, and the heating rate is 3 °C / min. After furnace cooling to 300 °C, air cool to 25 °C, and quickly store the obtained powder material in an argon atmosphere to obtain the positive electrode material to be prepared.

[0041] Example 4 This example is used to illustrate the positive electrode material and its preparation method disclosed in the present invention, including most of the operating steps in Example 1. The difference is that the chemical formula of the positive electrode material is [Na 0.6 K 0.07 [Ni 0.4 Fe 0.15Mn 0.15 Cu 0.03 Ti 0.2 Co 0.02 Al 0.01 Mg 0.01 Zn 0.02 Sn 0.01 O 2 。

[0042] Examples 5 - 9 Examples 5 - 9 are used to illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1, and the difference lies in that the atomic ratio of each element in the chemical formula of the cathode material adopts the atomic ratio in Table 1.

[0043] Example 10 This example is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1, and the difference lies in that M is selected from chromium and cobalt, X is selected from yttrium, magnesium, and zinc, and the chemical formula of the cathode material is [Na 0.8 Li 0.07 [Ni 0.1 Fe 0.15 Mn 0.6 Cu 0.05 Ti 0.02 Co 0.02 Cr 0.01 Mg 0.02 Zn 0.02 Y 0.01 O 2 。 Comparative Example 1 Comparative Example 1 is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention. The cathode material in Comparative Example 1 is a commercially available NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 。

[0044] Comparative Example 2 Comparative Example 2 is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1, and the difference lies in that the chemical formula of the cathode material is Na 0.67 [Ni 0.2 Fe 0.2 Mn 0.2 Cu 0.2 Ti 0.2 O 2 。 Comparative Examples 3 - 5 Comparative Examples 3 to 5 are used to compare and illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference lies in that the atomic ratios of the elements in the chemical formula of the cathode material are the atomic ratios in Table 1.

[0045] Table 1 Performance Test The cathode materials prepared in the above Examples and Comparative Examples were used to prepare coin-type half-cells, and the specific capacity and performance at different rates were evaluated. The slurry was prepared according to the ratio of cathode active material: binder: conductive agent = 94:3:3 (mass ratio). Among them, the binder was PVDF, the conductive agent was SP, and NMP was used as the solvent. During the coin cell assembly, a GF / C glass fiber separator was used, a sodium sheet was used as the counter electrode, and an electrolyte based on NaPF 6 was used to assemble a CR2025 coin cell in a glove box. At room temperature, galvanostatic charge-discharge tests were carried out at current densities of 0.1C, 1C, and 5C (1C = 150 mA·g -1 ) in the voltage range of 2.0 - 4.2V. The test results are listed in Table 2.

[0046] Table 2 From the test results in Table 2, it can be seen that the present invention can prepare a cathode material with high capacity, good rate performance, and good cycling performance.

[0047] From the test results of Examples 1 to 10 and Comparative Example 3, it can be seen that when the atomic ratios of Ni, Fe, Mn, Cu, and Ti in the cathode material satisfy 0.85 ≤ a + b + c + d + e ≤ 0.95, and the atomic ratios of each element satisfy 0.05 ≤ a ≤ 0.4, 0.05 ≤ b ≤ 0.6, 0.1 ≤ c ≤ 0.7, 0.01 ≤ d ≤ 0.25, and 0.01 ≤ e ≤ 0.2, the cathode material has high capacity and good rate performance, resulting in good cycling performance of the battery.

[0048] From Examples 1 to 10 and Comparative Examples 1, 2, 4, and 5, it can be seen that when the cathode material contains both elements with ionic radii in the range of 40 - 70 pm and elements with ionic radii greater than or equal to 70 pm, it has high capacity and good rate performance, resulting in good cycling performance of the battery.

[0049] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that: The general formula of the positive electrode material is: [Na x A y ][Ni a Fe b Mn c Cu d Ti e M z X w ]O2, wherein, 0.6≤x≤1, 0≤y≤0.1, 0.05≤a≤0.4, 0.05≤b≤0.6, 0.1≤c≤0.7, 0.01≤d≤0.25, 0.01≤e≤0.2, 0.01<z<0.15, 0.01<w<0.1, a+b+c+d+e+z+w=1, A is selected from at least one of lithium and potassium, M is an element having an ionic radius of 40~70 pm, and X is an element having an ionic radius greater than or equal to 70 pm.

2. The positive electrode material according to claim 1, characterized in that 0.85≤a+b+c+d+e≤0.

95.

3. The positive electrode material according to claim 1, characterized in that The M is selected from at least two of aluminum, vanadium, chromium, molybdenum and cobalt.

4. The positive electrode material according to claim 1 or 3, characterized in that X is selected from at least three of magnesium, tin, zinc, gallium, germanium, niobium, zirconium, yttrium, antimony and calcium.

5. The positive electrode material according to claim 1, characterized in that The general formula of the positive electrode material is: [Na x A y ][Ni a Fe b Mn c Cu d Ti e Co f Al g Mg h Zn i Sn j ]O2, wherein 0.6≤x≤1, 0≤y≤0.1, 0.05≤a≤0.4, 0.05≤b≤0.6, 0.1≤c≤0.7, 0.01≤d≤0.25, 0.01≤e≤0.2, 0.01≤f<0.15, 0.01≤g<0.1, 0.01≤h<0.1, 0.01≤i<0.1, 0.01≤j<0.1, and A is selected from at least one of lithium and potassium.

6. The method for preparing a positive electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: According to [Na x A y ][Ni a Fe b Mn c Cu d Ti e M z X w ]O2, wherein the ratio is 0.6≤x≤1, 0≤y≤0.1, 0.05≤a≤0.4, 0.05≤b≤0.6, 0.1≤c≤0.7, 0.01≤d≤0.25, 0.01≤e≤0.2, 0.01<z<0.15, 0.01<w<0.1, adding a sodium source, a lithium source, a potassium source, a nickel source, an iron source, a manganese source, a copper source, a titanium source, a compound containing the element M and a compound containing the element X into a solvent and stirring to obtain a metal salt solution that is uniformly mixed at an ionic scale; Dropping the metal salt solution into the solution containing the chelating agent, continuously stirring and evaporating the solvent, and then drying to obtain a positive electrode precursor material; The positive electrode precursor material is heat treated and cooled to obtain a positive electrode material.

7. The method for preparing the positive electrode material according to claim 6, characterized in that: The heat treatment comprises the following steps: The positive electrode precursor material is pre-sintered, and the temperature is increased to 480-550° C. at a heating rate of 3-5° C. / min for sintering for 6-8 hours; The cathode precursor material after initial sintering is cooled and then coarsely ground to obtain a solid powder; The solid powder is subjected to final calcination, and the temperature is increased to 850-1000° C. at a heating rate of 3-5° C. / min for sintering, and the sintering time is 12 h to 20 h. The powder is cooled to obtain a positive electrode material.

8. The method for preparing the positive electrode material according to claim 6, characterized in that: The sodium source includes at least one of sodium carbonate, sodium citrate and sodium oxalate; The lithium source includes at least one of lithium acetate, lithium oxalate and lithium carbonate; The potassium source includes at least one of potassium acetate, potassium oxalate and potassium carbonate; The nickel source includes at least one of nickel acetate and nickel oxalate; The iron source includes at least one of ferric acetate, ferric oxalate and ferric nitrate; The manganese source includes at least one of manganese acetate, manganese oxalate and manganese dioxide; The copper source includes at least one of copper acetate and copper oxalate; The titanium source includes at least one of titanium acetate, titanium oxalate, and titanate; And / or, the chelating agent includes at least one of ethylenediaminetetraacetic acid, citric acid, glycolic acid, and acrylic acid.

9. A positive electrode sheet, characterized in that: It comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode material according to any one of claims 1 to 5, or the positive electrode active material layer comprises the positive electrode material prepared by the preparation method according to any one of claims 6 to 8.

10. A battery, characterized in that: Including the positive electrode sheet as described in claim 9.

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