Single-crystal sodium-electric positive electrode material and preparation method and application thereof

Abstract

The application discloses a single-crystal sodium battery positive electrode material, wherein the sodium battery positive electrode material is Na a Ni b Cu c Mn d Ti e Me f O2, in an XRD diffraction peak spectrum of the sodium battery positive electrode material, a relative intensity I (012) / I (003) of a (012) crystal face to a (003) crystal face is 0.04-0.44, a relative intensity I (104) / I (003) of a (104) crystal face to the (003) crystal face is 0.14-1.14, and a relative intensity I (012) / I (104) of the (012) crystal face to the (104) crystal face is 0.28-0.38. The sodium battery positive electrode material is used in a battery, and the battery has more stable results in a high-voltage cycle process, thereby being beneficial to improving cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of materials, specifically to a single-crystal sodium cathode material, its preparation method, and its application. Background Technology

[0002] Technology changes lives. The diversification of electronic product applications has transformed our lifestyles, making our lives more convenient. While lithium-ion batteries are commonly used in current electronic products, research on sodium-ion batteries is also increasing with advancements in battery technology. Firstly, sodium is abundant; it is one of the most abundant metallic elements on Earth, with an abundance of 2.64% in the Earth's crust, 440 times that of lithium. Sodium resources are widely distributed and easy to refine, eliminating concerns about supply shortages or price fluctuations. Secondly, sodium-ion batteries are inexpensive. The positive electrode material does not require the relatively expensive metals lithium, nickel, and cobalt, and the negative electrode can use cheaper aluminum foil (lithium batteries use copper foil). The material cost of sodium-ion batteries is 30%-40% lower than that of lithium-ion batteries.

[0003] O3-type sodium-ion cathode materials have become a research hotspot since their inception due to their high specific capacity and ease of synthesis. Especially since Japanese scientist Komaba assembled the first sodium-ion full cell with hard carbon, it has attracted global attention and sparked a new wave of rapid development in sodium-ion batteries. However, they also suffer from poor air stability, complex phase transitions, and poor cycle performance under high voltage, severely hindering their commercial application. While some researchers have managed to suppress complex phase transitions through doping and other methods, improvements in the cycle performance of sodium-ion cathode materials under high voltage remain limited, especially for planar O3-type sodium-ion cathode materials. Studies have found that different methods of obtaining sodium-ion cathode materials lead to different exposed crystal planes. The intensity of high-energy crystal planes not only affects the crystal morphology but also the structural stability of the sodium-ion cathode material. However, while existing technologies can improve the stability of sodium-ion cathode materials to some extent by adjusting the intensity of only one high-energy crystal plane, they also cause the sodium-ion cathode material to have a single crystal orientation, thereby affecting the basic morphology of the crystal and ultimately the electrical performance of the sodium-ion cathode material. Summary of the Invention

[0004] This invention addresses the problems in the prior art by disclosing a single-crystal sodium-ion cathode material. The single-crystal sodium-ion cathode material prepared by the method of this invention has good structural stability, and when the sodium-ion cathode material of this invention is used in a battery, the battery exhibits good cycle performance under high voltage.

[0005] This invention is achieved through the following technical solution:

[0006] A single-crystal sodium battery cathode material provided by the present invention, the sodium battery cathode material is Na a Ni b Cu c Mn d Ti e Me f O2, where Na represents sodium, Ni represents nickel, Cu represents copper, Mn represents manganese, Ti represents titanium, O represents oxygen, and Me is selected from one or more elements of Li (lithium), B (boron), Mg (magnesium), Al (aluminum), Si (silicon), Ca (calcium), Zr (zirconium), Zn (zinc), Ta (tantalum), Mo (molybdenum), W (tungsten), La (lanthanum), Sr (strontium), Sb (antimony); where the selection of 0.9 ≤ a ≤ 0.95, 0 < b < 0.5, 0 < c < 0.3, 0 < d < 0.5, 0 < e < 0.2, 0 ≤ f < 0.1; in the XRD diffraction peak pattern of the sodium battery cathode material, the relative intensity I (012) / I (003) of the (012) crystal plane and the (003) crystal plane is 0.04 - 0.44, the relative intensity I (104) / I (003) of the (104) crystal plane and the (003) crystal plane is 0.14 - 1.14, and the relative intensity I (012) / I (104) of the (012) crystal plane and the (104) crystal plane is 0.28 - 0.38.

[0007] In the above design of the present invention, the stoichiometric value of sodium in the structure of the sodium battery cathode material of the present invention is less than 1 and greater than 0.8, which can improve the occupancy of Ni, Cu, Mn, and Ti in the sodium battery cathode material structure. The dispersion between Ni, Cu, Mn, and Ti in the structure of the sodium battery cathode material is better, and they can be evenly dispersed in the sodium battery cathode material, laying a foundation for further adjusting the crystal plane strength of the sodium battery cathode material in this case. The ratio between Ni, Cu, Mn, and Ti in the present invention promotes that in the sodium battery cathode material, the relative intensity I (012) / I (003) of the (012) crystal plane and the (003) crystal plane is 0.04 - 0.44, the relative intensity I (104) / I (003) of the (104) crystal plane and the (003) crystal plane is 0.14 - 1.14, and the relative intensity I (012) / I (104)The relative crystal plane intensity of the sodium-ion cathode material of this invention is within this range (0.28-0.38). While maintaining the crystal morphology of the sodium-ion cathode material, this invention further addresses the problem of numerous side reactions under high voltage, reduces the dissolution of transition metals, and is beneficial to the capacity and structural stability of the sodium-ion cathode material. It also improves the stability of the sodium-ion cathode material, facilitating the deintercalation and intercalation of sodium ions under high voltage, thereby enhancing the cycle performance of the sodium-ion cathode material under high voltage. Furthermore, during battery charging and discharging, Cu and Ni in the sodium-ion cathode material structure compensate for charge through reversible redox reactions, thus improving battery capacity. Mn and Ti stabilize the framework structure, contributing to structural stability during battery cycling. In addition, the combined effect of Cu and Ti effectively suppresses complex phase transitions, effectively improving average voltage and air stability. Ti also helps release stress during the interlayer deintercalation and intercalation of sodium ions, alleviating pressure with lower volumetric strain, which is beneficial to improving structural stability under high sodium deintercalation conditions. Therefore, the sodium-ion cathode material of this invention, under the above design, can improve the electrical performance of the battery.

[0008] In this invention, the intensity of the (012) crystal plane refers to the peak intensity of the (012) crystal plane in the XRD diffraction peak pattern; the intensity of the (003) crystal plane refers to the peak intensity of the (003) crystal plane in the XRD diffraction peak pattern; and the intensity of the (104) crystal plane refers to the peak intensity of the (104) crystal plane in the XRD diffraction peak pattern.

[0009] As a further option, the sodium-ion battery cathode material is Na. a Ni b Cu c Mn d Ti e Me f O2, wherein Na represents sodium, Ni represents nickel, Cu represents copper, Mn represents manganese, Ti represents titanium, O represents oxygen, and Me is selected from one or more elements among Li (lithium), B (boron), Mg (magnesium), Al (aluminum), Si (silicon), Ca (calcium), Zr (zirconium), Zn (zinc), Ta (tantalum), Mo (molybdenum), W (tungsten), La (lanthanum), Sr (strontium), and Sb (antimony); wherein 0.9≤a≤0.95, 0.38≤b≤0.4, 0.1≤c<0.3, 0.38≤d≤0.4, 0.1≤e<0.2, and 0≤f<0.1 are selected; in the XRD diffraction peak pattern of the sodium-ion cathode material, the relative intensity I of the (012) crystal plane and the (003) crystal plane is... (012) / I (003) The relative intensity I between the (104) and (003) crystal planes is 0.04-0.44. (104) / I (003)The relative intensity I between the (012) and (104) crystal planes is 0.14-1.14. (012) / I (104) It ranges from 0.28 to 0.38.

[0010] As a further embodiment, the tap density of the sodium-ion battery cathode material is not less than 1.7 g / cm³. 3 The specific surface area of ​​the sodium-ion battery cathode material is less than 0.3 m². 2 / g.

[0011] As a further embodiment, the sodium-ion battery cathode material has a plate-like crystal morphology.

[0012] The present invention also provides a method for preparing the sodium-ion cathode material, the method comprising:

[0013] The sodium-ion cathode material precursor and sodium source are sintered at a sintering temperature of 900℃-1100℃ for 13h-17h, with an oxygen flow rate of 0.3L / min-0.7L / min. The ratio of Na stoichiometry in the sodium source to the total stoichiometry of Cu, Ni, Mn, and Ti elements in the sodium-ion cathode material precursor is 0.9-0.95:1, yielding the sodium-ion cathode material of this invention. In the method of this invention, by coordinating sodium content, sintering temperature, and oxygen flow rate, the relative strengths of the (003), (012), and (104) crystal planes of the obtained sodium-ion cathode material are within the range of this invention. Specifically: the (012) crystal plane has higher surface energy, which is mainly controlled by adjusting the oxygen flow rate and sodium content; the strength of the (003) crystal plane is mainly controlled by the sintering temperature; and the strength of the (104) crystal plane is mainly controlled by the oxygen flow rate.

[0014] As a further option, the sodium-ion battery cathode material precursor is [Ni g Cu h Mn i Ti j Me k ]O 2+β In this system, Ni represents nickel, Cu represents copper, Mn represents manganese, Ti represents titanium, O represents oxygen, and Me is selected from one or more of Li (lithium), B (boron), Mg (magnesium), Al (aluminum), Si (silicon), Ca (calcium), Zr (zirconium), Zn (zinc), Ta (tantalum), Mo (molybdenum), W (tungsten), La (lanthanum), Sr (strontium), and Sb (antimony); where g+h+i+j+k=1, and α×(g+h+i+j+k)=2×(2+β), where α is the average valence of Ni, Cu, Mn, Ti, and Me; and 0 <g≤0.9;0<h≤0.5;0<i≤0.9;0≤j≤0.67;0≤k;-0.02≤β≤0.02。

[0015] As a further embodiment, the sodium source includes one or more of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium acetate.

[0016] As a further option, the heating rate to reach the sintering temperature is 1.5℃ / min-2.5℃ / min.

[0017] As a further step, in order to promote the full sintering of the sodium source and sodium-ion cathode material precursor, we can break the sintered material during the sintering process. The purpose of breaking is to expose the interior of the particles, which is conducive to the complete sintering of the product and thus to obtaining sodium-ion cathode material with better product consistency.

[0018] As a further embodiment, the product obtained after sintering in this invention needs to be cooled to room temperature. Natural cooling can be used, or the temperature of the product can be reduced at a certain cooling rate, which can be selected as 1.5℃ / min-2.5℃ / min.

[0019] The present invention also provides the application of the sodium electrode material in batteries or electrochemical devices.

[0020] The present invention also provides the application of the battery or electrochemical device in electrical equipment.

[0021] As a further option, the electrical equipment includes large electrical equipment and small electrical equipment.

[0022] As a further embodiment, the large electrical equipment includes transportation electrical equipment; the small electrical equipment includes end-consumer products, wearable electronic devices, or portable electronic devices.

[0023] As a further option, the transportation equipment includes automobiles, motorcycles, electric bicycles, buses, subways, high-speed trains, airplanes, and ships.

[0024] As a further option, the end-consumer products include mobile phones, laptops, pen input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, and portable printers.

[0025] As a further embodiment, the wearable electronic device or portable electronic device includes a stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini CD, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a drone, a motor, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a sodium-ion capacitor.

[0026] The features and beneficial effects of this invention are as follows:

[0027] (1) The present invention obtains sodium-ion cathode material for use in batteries, and the batteries have more stable results during high-voltage cycling, which is beneficial to improving the cycle performance of batteries.

[0028] (2) The present invention provides sodium electrode material with good stability in air.

[0029] (3) The sodium electrode material obtained by the method of the present invention has good consistency and good morphology.

[0030] (4) The sodium-ion cathode material obtained by this invention can be used in batteries, and the capacity retention rate of the battery after 50 cycles at an operating voltage of 2V-4.5V is not less than 85%. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a characteristic peak diagram of the XRD pattern in an embodiment of the present invention.

[0033] Figure 2 This is the first charge-discharge curve of an embodiment of the present invention.

[0034] Figure 3 This is a SEM image from an embodiment of the present invention.

[0035] Figure 4 This is a schematic diagram of the morphology of an embodiment of the present invention. Detailed Implementation

[0036] To facilitate understanding of the single-crystal sodium cathode material of the present invention, a more comprehensive description of the preparation method of the single-crystal sodium cathode material of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0037] The method for preparing sodium-ion battery cathode material precursors of the present invention is not limited to the preparation of sodium-ion battery cathode materials as illustrated in the examples of the present invention; the present invention only provides an example method for preparing a precursor sodium-ion battery cathode material. Those skilled in the art can also utilize commercially available methods.

[0038] Preparation method of sodium-ion battery cathode material precursor: Based on Cu element, Ni element, Mn element, Ti element, and Me element, according to the stoichiometric ratios of Cu element, Ni element, Mn element, Ti element, and Me element in the designed sodium-ion battery cathode material, soluble salts containing Cu, Ni, Mn, Ti, and Me are weighed respectively, and then the soluble salts are dissolved in deionized water, and carbonate and complexing agent are added for coprecipitation. The complexing agents can be oxalic acid, ammonia water, EDTA (ethylenediaminetetraacetic acid), urea, sodium citrate, hydroxycarboxylate, citric acid, etc. In this example, citric acid is used as the main complexing agent to prevent the precipitation of elements with different solubility product constants from deviating from the chemical ratio. The concentration of citric acid is 0.2 mol / L. In the example, sodium carbonate is selected as the carbonate, and the concentration of sodium carbonate in this invention is 2 mol / L. The pH of the solution is adjusted by the precipitating agent sodium carbonate, and the pH environment of the coprecipitation is controlled to be 8 - 8.5, and the stirring speed is 600 r / min, and the obtained sodium-ion battery cathode material precursor is [Ni g Cu h Mn i Ti j Me k O 2+β , where Me is selected from one or more of Li, B, Mg, Al, Si, Ca, Zr, Zn, Ta, Mo, W, La, Sr, Sb; where g + h + i + j + k = 1, and α×(g + h + i + j + k) = 2×(2 + β), where α is the average valence of Ni, Cu, Mn, Ti, and Me; where 0 < g ≤ 0.9; 0 < h ≤ 0.5; 0 < i ≤ 0.9; 0 ≤ j ≤ 0.67; 0 ≤ K; -0.02 ≤ β ≤ 0.02. Based on Cu element, Ni element, Mn element, Ti element, and Me element, according to the stoichiometric ratio of the sodium-ion battery cathode material, soluble salts of Cu, Ni, Mn, Ti, and Me are weighed respectively, and the sodium-ion battery cathode material precursor is obtained by the above method.

[0039] Example 1: Based on molar mass, the ratio of the stoichiometric ratio of Na element in the sodium source to the total stoichiometric ratio of Cu element, Ni element, Mn element, and Ti element in the sodium-ion battery cathode material precursor is 0.9:1. The sodium-ion battery cathode material precursor and the sodium source (sodium carbonate) are weighed according to the calculated ratio, and the obtained sodium-ion battery cathode material precursor and the sodium source are sintered at 950 °C for 15 h, crushed, and then sintered at 950 °C for 15 h again. The oxygen flow rate during sintering is 0.315 L / min, and the obtained sodium-ion battery cathode material is Na 0.9 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0040] Example 2: The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.92:1. The sodium-ion cathode material precursor and sodium source are weighed according to this calculated ratio. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.315 L / min. The resulting sodium-ion cathode material is Na... 0.92 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0041] Example 3: The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.95:1. The sodium-ion cathode material precursor and sodium source are weighed according to this calculated ratio. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.315 L / min. The resulting sodium-ion cathode material is Na... 0.95 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0042] Example 4: The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.9:1. The sodium-ion cathode material precursor and sodium source are weighed according to this calculated ratio. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 1000℃ for 15 hours, broken up, and then sintered again at 1000℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na… 0.9 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0043] Example 5: The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.92:1. The sodium-ion cathode material precursor and sodium source are weighed according to this calculated ratio. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 1000℃ for 15 hours, broken up, and then sintered again at 1000℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na... 0.92 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0044] Example 6: The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.95:1. The sodium-ion cathode material precursor and sodium source are weighed according to this calculated ratio. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 1000℃ for 15 hours, broken up, and then sintered again at 1000℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na… 0.95 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0045] Example 7: The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.9:1. The sodium-ion cathode material precursor and sodium source are weighed according to this calculated ratio. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 1050℃ for 15 hours, broken up, and then sintered again at 1050℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na… 0.9 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0046] Example 8:

[0047] The preparation of the sodium-ion battery cathode material precursor in Example 8 was as follows:

[0048] Copper sulfate (calculated as copper), nickel sulfate (calculated as nickel), manganese sulfate (calculated as manganese), and titanium oxysulfate (calculated as titanium) were weighed according to the stoichiometry of the sodium-ion battery cathode material. A 2 mol / L sulfate mixed solution was prepared, using sodium citrate as a complexing agent (0.6 mol / L citrate concentration) and sodium carbonate as a precipitant, adjusting the pH of the precipitation to 7.8-8.3. The particle size D50 of the co-precipitated material was controlled to approximately 5 μm. After washing to remove impurities, the precipitate was dehydrated at 700℃ to obtain the precursor for the sodium-ion battery cathode material.

[0049] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.9:1. Using this calculated ratio, the sodium-ion cathode material precursor and sodium source are weighed separately. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na... 0.9 Cu 2 / 18 Ni 7 / 18 Mn 7 / 18 Ti 2 / 18 O2.

[0050] Example 9:

[0051] The preparation method of the sodium-ion cathode material precursor in Example 9 is the same as that in Example 8.

[0052] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.95:1. Using this calculated ratio, the sodium-ion cathode material precursor and sodium source are weighed separately. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na... 0.95 Cu 2 / 18 Ni 7 / 18 Mn 7 / 18 Ti 2 / 18 O2.

[0053] Example 10:

[0054] The preparation method of the sodium-ion cathode material precursor in Example 10 is the same as that in Example 8.

[0055] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 0.9:1. Using this calculated ratio, the sodium-ion cathode material precursor and sodium source are weighed separately. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na... 0.9 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0056] Comparative Example 1:

[0057] The preparation method of the sodium-ion cathode material precursor in Comparative Example 1 is the same as that in Examples 1-7.

[0058] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 1:1. Using this calculated ratio, the sodium-ion cathode material precursor and sodium source are weighed separately. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na... 1.0 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0059] Comparative Example 2:

[0060] The preparation method of the sodium-ion cathode material precursor in Comparative Example 2 is the same as that in Examples 1-7.

[0061] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion battery cathode material precursor is 1:1. Using this calculated ratio, the sodium-ion battery cathode material precursor and sodium source are weighed separately. The resulting sodium-ion battery cathode material precursor and sodium source (sodium carbonate) are sintered at 1000℃ for 15 hours, broken up, and then sintered again at 1000℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion battery cathode material is Na... 1.0 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0062] Comparative Example 3:

[0063] The preparation method of the sodium-ion cathode material precursor in Comparative Example 3 is the same as that in Examples 1-7.

[0064] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 1:1. Using this calculated ratio, the sodium-ion cathode material precursor and sodium source are weighed separately. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.315 L / min. The resulting sodium-ion cathode material is Na... 1.0 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0065] Comparative Example 4:

[0066] The preparation method of the sodium-ion cathode material precursor in Comparative Example 4 is the same as that in Examples 1-7.

[0067] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion battery cathode material precursor is 1:1. Using this calculated ratio, the sodium-ion battery cathode material precursor and sodium source are weighed separately. The resulting sodium-ion battery cathode material precursor and sodium source (sodium carbonate) are sintered at 1000℃ for 15 hours, broken up, and then sintered again at 1000℃ for 15 hours. The oxygen flow rate during sintering is 0.315 L / min. The resulting sodium-ion battery cathode material is Na… 1.0 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0068] Comparative Example 5:

[0069] The preparation method of the sodium-ion battery cathode material precursor in Comparative Example 5 includes: copper sulfate (calculated as copper), nickel sulfate (calculated as nickel), manganese sulfate (calculated as manganese), and titanium oxysulfate (calculated as titanium). According to the stoichiometric ratio of the sodium-ion battery cathode material, copper sulfate, nickel sulfate, manganese sulfate, and titanium oxysulfate are weighed separately to prepare a 2 mol / L sulfate mixed solution. Sodium citrate is used as a complexing agent, with a citrate concentration of 0.6 mol / L. Sodium carbonate is used as a precipitant, and the pH of the precipitation is adjusted to 7.8-8.3. The particle size D50 of the co-precipitated material is controlled to be approximately 5 μm. After washing to remove impurities, the precipitated material is dehydrated at 700℃ to obtain the sodium-ion battery cathode material precursor.

[0070] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 1:1. Using this calculated ratio, the sodium-ion cathode material precursor and sodium source are weighed separately. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na... 1.0 Cu 0.1 Ni 0.35 Fe 0.1 Mn 0.35 Ti 0.1 O2.

[0071] Comparative Example 6:

[0072] The preparation method of the sodium-ion cathode material precursor in Comparative Example 6 is the same as that in Comparative Example 5.

[0073] The molar mass ratio of Na in the sodium source to the total molar mass ratio of Cu, Ni, Mn, and Ti in the sodium-ion cathode material precursor is 1:1. Using this calculated ratio, the sodium-ion cathode material precursor and sodium source are weighed separately. The resulting sodium-ion cathode material precursor and sodium source (sodium carbonate) are sintered at 950℃ for 15 hours, broken up, and then sintered again at 950℃ for 15 hours. The oxygen flow rate during sintering is 0.63 L / min. The resulting sodium-ion cathode material is Na... 1.0 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0074] We also obtained sodium-ion cathode material for use in half-coin cells and conducted a series of electrical performance tests on the cells, including:

[0075] Battery fabrication process: The positive electrode material is used as the positive electrode active material. Conductive carbon (Super P) and binder PVDF (polyvinylidene fluoride) are coated on aluminum foil in a mass ratio of 90:5:5. The foil is then cut into circular pieces with a diameter of 12 mm and a charge loading of 5-6 mg / cm³. 2After vacuum drying, half-cells were prepared using CR2032 coin cells in an argon-filled glove box. The counter electrode was metallic sodium, the electrolyte was 1M NaClO4 (sodium perchlorate) electrolyte salt, and the solvent was a 1:1 volume ratio of PC (ethylene carbonate) / DEC (diethyl carbonate) electrolyte with 2% FEC (fluoroethylene carbonate) added. The tests were conducted in a voltage window of 2-4.3V with a current density of 10mAh / g, and the cells were charged first and then discharged.

[0076] Validation Result Analysis

[0077] Table 1 Test results of embodiments and comparative examples of the present invention

[0078]

[0079] Sodium-ion cathode material was successfully obtained using the preparation method of this invention. The sodium-ion cathode material obtained by this invention has a plate-like crystal morphology, such as... Figures 3-4 As shown. We used the sodium-ion battery cathode material obtained in this invention in a battery, and it exhibited good cycle performance at operating voltages of 2V-4.3V. As can be seen from Table 1, Examples 1-10 all showed a cycle performance of no less than 85%. We believe this is mainly because we obtained a relative strength I between the (012) and (003) crystal planes of the sodium-ion battery cathode material. (012) / I (003) The relative intensity I between the (104) and (003) crystal planes is 0.04-0.44. (104) / I (003) The relative intensity I between the (012) and (104) crystal planes is 0.14-1.14. (012) / I (104) The relative crystal strength is 0.28-0.38. When the relative crystal plane strength of the sodium-ion cathode material is within this range, it not only maintains the crystal morphology of the sodium-ion cathode material, but also reduces side reactions under high voltage and decreases the dissolution of transition metals in the sodium-ion cathode material, which is beneficial to the stability of the battery capacity and structure. Moreover, sodium-ion cathode materials with this crystal plane strength can also improve the insertion / extraction of sodium ions in the sodium-ion cathode material under high voltage, thereby improving the cycle performance and charge / discharge specific capacity of the sodium-ion cathode material. We can verify this by comparing Examples 1-10 with Comparative Examples 1-6. The electrical performance of Examples 1-12 of the present invention is better than that of Comparative Examples 1-6. It can be seen that the sodium-ion cathode material obtained by the present invention can be used in high-voltage working environments and can improve the electrical performance of the battery.

[0080] How do we control the relative intensity of crystal planes in sodium-ion cathode materials? We verified this by designing Examples 1-10 and Comparative Examples 1-6.

[0081] Through the preparation method of this invention, the exposure of the crystal faces of the sodium-ion cathode material is mainly controlled by the main factors, with other factors playing a supporting and combined regulatory role. However, the final exposure trend of the crystal faces still mainly stems from the regulatory effect of the main factors. In the preparation method of this invention, the sodium content, oxygen content, sintering temperature, and other major elements in the sodium-ion cathode material play a more important role in directly influencing the exposure of the (012), (003), and (104) crystal faces. To this end, we verified this through Examples 1-10.

[0082] First, by comparing Examples 1-12 with Comparative Examples 1-6, we can see that by adjusting the ratio between the sodium-ion cathode material precursor and the sodium source, a sodium-depleted sodium-ion cathode material can be obtained. The crystal planes of this sodium-depleted sodium-ion cathode material are exposed within the relative intensity range of this invention. We believe this may be because the sodium-depleted sodium-ion cathode material structure can increase the occupancy of Cu, Mn, Ni, and Ti in the sodium-ion cathode material structure, thus promoting the acquisition of a sodium-ion cathode material with crystal plane intensity within the scope of this invention.

[0083] We also found that the sodium-ion battery cathode material structure contains Cu, Ni, Mn, and Ti, and these substances can be uniformly dispersed in the structure, thus preparing for the regulation of the relative crystal plane intensity of the sodium-ion battery cathode material. Comparison of Examples 6 and 9, and Examples 8 and 10, revealed that by changing the proportions of Cu, Ni, Mn, and Ti in the structure of the sodium-ion battery cathode material, the crystal plane exposure of the sodium-ion battery cathode material can be further improved. Increasing the proportions of Cu and Ti while decreasing the proportions of Mn and Ni can promote an increase in the exposure of the (012) crystal plane.

[0084] Based on this, we further compared Examples 1-3 and found that the exposure of the (012) crystal plane in the sodium-ion cathode material can be mainly adjusted by increasing the Na content. We can see that, compared with Examples 1-3, the exposure of the (012) crystal plane decreases with the increase of Na content. We can verify our results by comparing Examples 4-6 and Examples 8-9.

[0085] Based on this, we further compared Examples 1 and 10 and found that the exposure of the (012) and (014) crystal planes in the sodium-ion cathode material can be mainly adjusted by regulating the oxygen flow rate. Comparing Examples 7 and 10, we found that the exposure of the (003) crystal plane in the sodium-ion cathode material can be mainly adjusted by regulating the sintering temperature. We further verified this by comparing Examples 1 with Examples 4, Examples 2 with Examples 5, and Examples 3 with Examples 6. We found that in Examples 4-6, when both temperature and oxygen content increase simultaneously, the oxygen flow rate mainly regulates the exposure of the (012) and (014) crystal planes in the sodium-ion cathode material, while the sintering temperature mainly regulates the exposure of the (003) crystal plane. Therefore, Examples 4-6 exhibit a relative intensity I between the (012) and (003) crystal planes. (012) / I (003) As the crystal plane increases, the relative intensity I between the (012) and (104) crystal planes increases. (012) / I (104) The relative intensity I between the (104) crystal plane and the (003) crystal plane (104) / I (003) It is decreasing.

[0086] In summary, the sodium-ion cathode material obtained by this invention can be used in batteries and exhibits good cycle performance and capacity under high voltage.

[0087] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A single-crystal sodium cathode material, characterized in that, The sodium-ion cathode material is Na a Ni b Cu c Mn d Ti e Me f O2, where Na represents sodium, Ni represents nickel, Cu represents copper, Mn represents manganese, Ti represents titanium, O represents oxygen, and Me is selected from one or more elements of Li, B, Mg, Al, Si, Ca, Zr, Zn, Ta, Mo, W, La, Sr, Sb; where 0.9 ≤ a ≤ 0.95, 0 < b < 0.5, 0 < c < 0.3, 0 < d < 0.5, 0 < e < 0.2, 0 ≤ f < 0.1; in the XRD diffraction peak pattern of the sodium-ion cathode material, the relative intensity I (012) / I (003) of the (012) crystal plane and the (003) crystal plane is 0.2 - 0.44, the relative intensity I (104) / I (003) of the (104) crystal plane and the (003) crystal plane is 0.62 - 1.14, and the relative intensity I (012) / I (104) of the (012) crystal plane and the (104) crystal plane is 0.28 - 0.

39.

2. The single-crystal sodium cathode material according to claim 1, characterized in that, The sodium electrode material is Na. a Ni b Cu c Mn d Ti e Me f O2, where Na represents sodium, Ni represents nickel, Cu represents copper, Mn represents manganese, Ti represents titanium, O represents oxygen, and Me is selected from one or more elements from Li, B, Mg, Al, Si, Ca, Zr, Zn, Ta, Mo, W, La, Sr, and Sb; where 0.9≤a≤0.95, 0.38≤b≤0.4, 0.1≤c<0.3, 0.38≤d≤0.4, 0.1≤e<0.2, and 0≤f<0.1; in the XRD diffraction peak pattern of the sodium-ion cathode material, the relative intensity I of the (012) crystal plane and the (003) crystal plane is... (012) / I (003) The relative intensity I between the (104) and (003) crystal planes is 0.2-0.

44. (104) / I (003) The relative intensity I between the (012) and (104) crystal planes is 0.62-1.

14. (012) / I (104) It ranges from 0.28 to 0.

39.

3. The single-crystal sodium cathode material according to claim 1, characterized in that, The sodium-ion cathode material exhibits characteristic diffraction peaks at 16.5°, 33.4°, 35.4°, 36.7°, 41.7°, and 45.1° in its X-ray powder diffraction pattern, expressed as a diffraction angle of 2θ.

4. The single-crystal sodium cathode material according to claim 1, characterized in that, The tap density of the sodium-ion battery cathode material is not less than 1.7 g / cm³. 3 The specific surface area of ​​the sodium-ion battery cathode material is less than 0.3 m². 2 / g.

5. The single-crystal sodium cathode material according to claim 1, characterized in that, The sodium-ion cathode material has a plate-like crystal morphology.

6. The method for preparing the single-crystal sodium cathode material according to any one of claims 1-5, characterized in that, The sodium-ion cathode material precursor and sodium source were sintered at a sintering temperature of 900℃-1100℃ for 13h-17h with an oxygen flow rate of 0.3L / min-0.7L / min. The ratio of the stoichiometric ratio of Na in the sodium source to the total stoichiometric ratio of Cu, Ni, Mn and Ti in the sodium-ion cathode material precursor was 0.9-0.95:1, in terms of molar mass, to obtain the sodium-ion cathode material.

7. The preparation method according to claim 6, characterized in that, The sodium-ion cathode material precursor is [Ni g Cu h Mn i Ti j Me k ]O 2+β In this system, Ni represents nickel, Cu represents copper, Mn represents manganese, Ti represents titanium, O represents oxygen, and Me is selected from one or more of Li, B, Mg, Al, Si, Ca, Zr, Zn, Ta, Mo, W, La, Sr, and Sb; where g+h+i+j+k=1, and α×(g+h+i+j+k)=2×(2+β), where α is the average valence of Ni, Cu, Mn, Ti, and Me; and 0 <g≤0.9;0<h≤0.5;0<i≤0.9;0≤j≤0.67;0≤k;-0.02≤β≤0.02。 8. The preparation method according to claim 6, characterized in that, The sodium source includes one or more of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium acetate.

9. The preparation method according to claim 6, characterized in that, The heating rate to reach the sintering temperature is 1.5℃ / min-2.5℃ / min.

10. An electrochemical device having a sodium electrode material according to any one of claims 1-5 or a sodium electrode material obtained by the preparation method according to any one of claims 6-9.

11. The electrochemical device according to claim 10, characterized in that, The electrochemical device is a battery, and the battery retains no less than 85% of its capacity after 50 cycles at a working voltage of 2V-4.5V.

Images