Monocrystalline sodium battery positive electrode material and preparation method and application thereof

Abstract

The invention discloses a single crystal sodium battery positive electrode material, the sodium battery positive electrode material is NaaNibCucMndTieMefO2, in an XRD (X-Ray Diffraction) peak pattern of the sodium battery positive electrode material, the relative intensity I (012) / I (003) of a (012) crystal face and a (003) crystal face is 0.04-0.44, the relative intensity I (104) / I (003) of a (104) crystal face and the (003) crystal face is 0.14-1.14, and the relative intensity I (012) / I (104) of the (012) crystal face and the (104) crystal face is 0.28-0.38. The obtained sodium battery positive electrode material is used in a battery, and the battery has a more stable result in a high-voltage cycle process, so that the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the field of materials, and in particular to a single crystal sodium cathode material and a preparation method and application thereof. Background Art

[0002] Technology is changing our lives. The diversification of electronic products is transforming our current lifestyles and making our lives more convenient. Lithium-ion batteries are commonly used in existing electronic products, but with the advancement of battery technology, research on sodium-ion batteries has also increased. Firstly, sodium is abundant. Sodium is one of the most abundant metal 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 simple to extract, eliminating the need for supply shortages or price fluctuations. Secondly, sodium-ion batteries are inexpensive. The positive electrode material for sodium-ion batteries does not require the relatively precious metals lithium, nickel, and cobalt, and the negative electrode can also 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 birth due to their advantages such as high specific capacity and easy synthesis. In particular, since Japanese scientist Komaba assembled the first sodium-ion full battery with hard carbon, it has attracted the follow-up of scientists around the world, triggering a new round of rapid development of sodium-ion batteries. However, it also has problems such as poor air stability, complex phase transitions, and poor cycle performance under high voltage, which seriously restrict its commercial application. Although some researchers in the existing technology can suppress complex phase transitions through doping and other methods, the improvement in the cycle performance of sodium-ion cathode materials under high voltage is still not obvious, especially for flat-plate O3-type sodium-ion cathode materials. Studies have found that the choice of different methods for obtaining sodium-ion cathode materials will result in different exposed crystal faces of the sodium-ion cathode materials. The crystal face strength of the high-energy face will not only affect the morphology of the crystal, but also affect the structural stability of the sodium-ion cathode material. However, the existing technology only adjusts the strength of one high-energy crystal plane of the sodium battery positive electrode material. Although it can improve the stability of the sodium battery positive electrode material to a certain extent, it will cause the crystal of the sodium battery positive electrode material to have a single orientation, thereby affecting the basic morphology of the crystal and ultimately affecting the electrical properties of the sodium battery positive electrode material. Summary of the Invention

[0004] In response to the problems in the prior art, the present invention discloses a single crystal sodium cathode material. The single crystal sodium cathode material obtained by the preparation method of the present invention has good structural stability. When the sodium cathode material of the present invention is used in a battery, the battery has good cycle performance under high voltage.

[0005] The present invention is achieved through the following technical solutions:

[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, and 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 the relative intensity I (012) / I (003) of the (012) crystal plane and the (003) crystal plane to be 0.04 - 0.44, the relative intensity I (104) / I (003) of the (104) crystal plane and the (003) crystal plane to be 0.14 - 1.14, and the relative intensity I (012) / I (104)The relative crystal plane strength of the sodium-ion cathode material of the present invention is within this range. On the basis of maintaining the crystal morphology of the sodium-ion cathode material, it further solves the problem of more 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; improves the stability of the sodium-ion cathode material, which is beneficial to the deintercalation of sodium ions in the sodium-ion cathode material under high pressure, thereby improving the cycle performance of the sodium-ion cathode material under high pressure. On this basis, during the battery charge and discharge process, the Cu and Ni in the sodium-ion cathode material structure compensate for the charge through reversible oxidation and reduction, which is beneficial to improving the capacity of the battery, while Mn and Ti play a role in stabilizing the framework structure, which is beneficial to the stability of the structure during the battery cycle. In addition, Cu and Ti can effectively suppress complex phase changes under the cooperation, which can effectively improve the average voltage and air stability, and Ti helps to release the stress of sodium ions in the interlayer deintercalation process, relieves the pressure with lower volume strain, and is beneficial to improving the structural stability under high sodium desorption state. It can be seen that the sodium-ion cathode material of the present invention can improve the electrical performance of the battery under the above design.

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

[0009] As a further solution, the sodium positive electrode 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 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); 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 spectrum of the sodium positive electrode material, the relative intensity I of the (012) crystal plane and the (003) crystal plane is (012) / I (003) The relative intensity of (104) crystal plane and (003) crystal plane is 0.04-0.44. (104) / I (003)The relative intensity of (012) crystal plane and (104) crystal plane is 0.14-1.14. (012) / I (104) It is 0.28-0.38.

[0010] As a further solution, the tap density of the sodium positive electrode material is not less than 1.7 g / cm 3 The specific surface area of ​​the sodium cathode material is less than 0.3 m 2 / g.

[0011] As a further solution, the crystal morphology of the sodium battery positive electrode material is flat.

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

[0013] The sodium cathode material precursor and the sodium source are sintered at a sintering temperature of 900° C. to 1100° C. for 13 h to 17 h, with an oxygen flow rate of 0.3 L / min to 0.7 L / min, wherein, in terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.9 to 0.95:1, thereby obtaining the sodium cathode material of the present invention. In the method of the present invention, by jointly adjusting the sodium content, sintering temperature, and oxygen flow rate, the relative strengths of the (003) crystal plane, the (012) crystal plane, and the (104) crystal plane of the sodium cathode material obtained by the present invention are within the scope of the present invention. Specifically, the (012) crystal plane has a higher surface energy, which is mainly adjusted by adjusting the oxygen flow rate and sodium content, the strength of the (003) crystal plane is mainly adjusted by the sintering temperature, and the strength of the (104) crystal plane is mainly adjusted by the oxygen flow rate.

[0014] As a further solution, the sodium cathode material precursor is [Ni g Cu h Mn i Ti j Me k ]O 2+β , wherein 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); wherein g+h+i+j+k=1, and α×(g+h+i+j+k)=2×(2+β), wherein α is the average valence of Ni, Cu, Mn, Ti, and Me; wherein 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 solution, the heating rate to reach the sintering temperature is 1.5°C / min-2.5°C / min.

[0017] As a further solution, in order to promote the full sintering of the sodium source and the sodium cathode material precursor, we can crush the sintered material during the sintering process. The purpose of the crushing is to expose the interior of the particles, which is conducive to the complete sintering of the product, thereby facilitating the acquisition of a sodium cathode material with better product consistency.

[0018] As a further solution, the product obtained after sintering in the present invention needs to be cooled to room temperature, which can be done by natural cooling or by cooling the product at a certain cooling rate, which can be selected from 1.5°C / min to 2.5°C / min.

[0019] The present invention also provides the use of the sodium cathode material in a battery or an electrochemical device.

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

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

[0022] As a further solution, the large-scale electrical equipment includes transportation electrical equipment; the small-scale electrical equipment includes terminal consumer products, wearable electronic devices or mobile electronic devices.

[0023] As a further solution, the electrical equipment for transportation includes automobiles, motorcycles, power-assisted bicycles, buses, subways, high-speed railways, airplanes, and ships.

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

[0025] As a further solution, the wearable electronic device or movable electronic device includes wearable stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, drones, motors, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and sodium ion capacitors.

[0026] The characteristics and beneficial effects of the present invention are:

[0027] (1) The sodium cathode material obtained by the present invention is used in batteries, and the battery has a more stable result during the cycle process under high voltage, which is beneficial to improving the cycle performance of the battery.

[0028] (2) The sodium cathode material obtained by the present invention has good stability in air.

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

[0030] (4) The sodium cathode material obtained by the present 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% BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

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

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

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

[0035] Figure 4 A schematic diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to facilitate understanding of the single crystal sodium cathode material of the present invention, the preparation method of the single crystal sodium cathode material of the present invention will be described in more detail below, and embodiments of the present invention are given, but the scope of the present invention is not limited thereby.

[0037] The method for preparing a sodium cathode material precursor of the present invention is not limited to the preparation of the sodium cathode material in the examples of the present invention. The present invention only provides an example of a method for preparing a sodium cathode material precursor. Those skilled in the art can also purchase it commercially.

[0038] Preparation method of precursor of sodium-ion battery cathode material: 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 carbonates and complexing agents 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 embodiment, 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 embodiment, 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. The obtained precursor of sodium-ion battery cathode material 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 ratios of the sodium-ion battery cathode material, soluble salts of Cu, Ni, Mn, Ti, and Me are weighed respectively, and the precursor of the sodium-ion battery cathode material is obtained by the above method.

[0039] Example 1: In terms of 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 precursor of the sodium-ion battery cathode material is 0.9:1. The precursor of the sodium-ion battery cathode material and the sodium source (sodium carbonate) are weighed according to the calculated ratio, and the obtained precursor of the sodium-ion battery cathode material and the sodium source are sintered at a sintering temperature of 950 °C for 15 h, crushed, and then sintered again at a sintering temperature of 950 °C for 15 h. The oxygen flow rate during sintering is 0.315 L / min, and the obtained sodium-ion battery cathode material is Na 0.9 Cu[[ID=1十八]] 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0040] Example 2: In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.92:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15h, crushed, and sintered again at a sintering temperature of 950°C for 15h. The oxygen flow rate during sintering is 0.315L / min, and the sodium cathode material is Na 0.92 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0041] Example 3: In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.95:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15h, crushed, and sintered again at a sintering temperature of 950°C for 15h. The oxygen flow rate during sintering is 0.315L / min, and the sodium cathode material is Na 0.95 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0042] Example 4: In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.9:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 1000°C for 15h, crushed, and sintered again at a sintering temperature of 1000°C for 15h. The oxygen flow rate during sintering is 0.63L / min, and the sodium cathode material is Na 0.9 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0043] Example 5: In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.92:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 1000° C. for 15 h, crushed, and sintered again at a sintering temperature of 1000° C. for 15 h. The oxygen flow rate during sintering is 0.63 L / min. The sodium cathode material is Na 0.92 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0044] Example 6: In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.95:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 1000°C for 15h, crushed, and sintered again at a sintering temperature of 1000°C for 15h. The oxygen flow rate during sintering is 0.63L / min, and the sodium cathode material is Na 0.95 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0045] Example 7: In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.9:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 1050°C for 15h, crushed, and sintered again at a sintering temperature of 1050°C for 15h. The oxygen flow rate during sintering is 0.63L / min, and the sodium 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 cathode material precursor in Example 8 is as follows:

[0048] Copper sulfate (calculated as copper element), nickel sulfate (calculated as nickel element), manganese sulfate (calculated as manganese element), and titanyl sulfate (calculated as titanium element) are weighed according to the stoichiometric ratio of the sodium cathode material. A 2 mol / L sulfate mixed solution is prepared. 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 precipitation pH 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°C to obtain a sodium cathode material precursor.

[0049] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.9:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15h, crushed, and sintered again at a sintering temperature of 950°C for 15h. The oxygen flow rate during sintering is 0.63L / min, and the sodium 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 cathode material precursor in Example 9 is the same as that in Example 8.

[0052] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.95:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15h, crushed, and sintered again at a sintering temperature of 950°C for 15h. The oxygen flow rate during sintering is 0.63L / min, and the sodium 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 cathode material precursor in Example 10 is the same as that in Example 8.

[0055] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.9:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15h, crushed, and sintered again at a sintering temperature of 950°C for 15h. The oxygen flow rate during sintering is 0.63L / min, and the sodium 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 cathode material precursor in Comparative Example 1 is the same as that in Examples 1 to 7.

[0058] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 1:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15 hours, crushed, and sintered again at a sintering temperature of 950°C for 15 hours. The oxygen flow rate during sintering is 0.63L / min, and the sodium cathode material obtained 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 cathode material precursor in Comparative Example 2 is the same as that in Examples 1 to 7.

[0061] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 1:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 1000°C for 15 hours, crushed, and sintered again at a sintering temperature of 1000°C for 15 hours. The oxygen flow rate during sintering is 0.63L / min, and the sodium cathode material obtained 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 cathode material precursor in Comparative Example 3 is the same as that in Examples 1 to 7.

[0064] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 1:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15 hours, crushed, and sintered again at a sintering temperature of 950°C for 15 hours. The oxygen flow rate during sintering is 0.315L / min, and the sodium cathode material obtained 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 cathode material precursor in Comparative Example 4 is the same as that in Examples 1 to 7.

[0067] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 1:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 1000°C for 15 hours, crushed, and sintered again at a sintering temperature of 1000°C for 15 hours. The oxygen flow rate during sintering is 0.315L / min, and the sodium cathode material obtained 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 cathode material precursor of Comparative Example 5 includes: copper sulfate is calculated as copper element, nickel sulfate is calculated as nickel element, manganese sulfate is calculated as manganese element, and titanyl sulfate is calculated as titanium element. According to the stoichiometric ratio of the sodium cathode material, copper sulfate, nickel sulfate, manganese sulfate, and titanyl sulfate are weighed respectively, and a 2 mol / L sulfate mixed solution is prepared. Sodium citrate is used as a complexing agent, wherein the citrate concentration is 0.6 mol / L, and sodium carbonate is used as a precipitant. The precipitation pH is regulated to 7.8-8.3. The particle size of the co-precipitated material D50 is controlled to be about 5 um. After washing to remove impurities, the precipitated material is dehydrated at 700 ° C to obtain a sodium cathode material precursor.

[0070] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 1:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15 hours, crushed, and sintered again at a sintering temperature of 950°C for 15 hours. The oxygen flow rate during sintering is 0.63L / min, and the sodium cathode material obtained 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 cathode material precursor of Comparative Example 6 is the same as that of Comparative Example 5.

[0073] In terms of molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 1:1. The sodium cathode material precursor and the sodium source are weighed according to the calculated ratio, and the obtained sodium cathode material precursor and the sodium source (sodium carbonate) are sintered at a sintering temperature of 950°C for 15 hours, crushed, and sintered again at a sintering temperature of 950°C for 15 hours. The oxygen flow rate during sintering is 0.63L / min, and the sodium cathode material obtained is Na 1.0 Cu 0.1 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0074] We also obtained sodium cathode materials for use in half-button batteries and conducted a series of electrical performance tests on the batteries. The testing process included:

[0075] Preparation process of the battery: The positive electrode material 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, and cut into 12mm diameter discs with a loading of 5-6mg / cm 2After vacuum drying, a half-cell was prepared using a CR2032 button cell in an argon glove box. Sodium metal was used as the counter electrode, 1M NaClO4 (sodium perchlorate) electrolyte salt was used as the electrolyte, and the solvent was a 1:1 volume ratio of PC (ethylene carbonate) to DEC (diethyl carbonate). 2% FEC (fluoroethylene carbonate) was added to the electrolyte. The test was conducted in a voltage window of 2-4.3 V with a current density of 10 mAh / g, with charge first followed by discharge.

[0076] Verification result analysis

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

[0078]

[0079] The sodium positive electrode material is successfully obtained by the preparation method of the present invention. The crystal morphology of the sodium positive electrode material obtained by the present invention is flat. Figure 3-Figure 4 As shown. We used the sodium cathode material obtained by the present invention in a battery, and it has good cycle performance at an operating voltage of 2V-4.3V. We can find from Table 1 that Examples 1 to 10 all show a cycle performance of not less than 85%. We believe that this is mainly because the relative strength of the (012) crystal plane and the (003) crystal plane of the sodium cathode material we obtained is I (012) / I (003) The relative intensity of (104) crystal plane and (003) crystal plane is 0.04-0.44. (104) / I (003) The relative intensity of (012) crystal plane and (104) crystal plane is 0.14-1.14. (012) / I (104) It is 0.28-0.38. When the relative crystal plane strength of the sodium-electric positive electrode material is within this range, first of all, on the basis of maintaining the crystal morphology of the sodium-electric positive electrode material, it can not only reduce the side reactions under high voltage and reduce the dissolution of transition metals in the sodium-electric positive electrode material, which is beneficial to the stability of the capacity and structure of the battery, but also the sodium-electric positive electrode material with this crystal plane strength can also be beneficial to improve the sodium ion deintercalation in the sodium-electric positive electrode material under high voltage, thereby improving the cycle performance and charge-discharge specific capacity of the sodium-electric positive electrode material. We can verify by comparing Examples 1 to 10 with Comparative Examples 1 to 6 that the electrical properties of Examples 1 to 12 of the present invention are better than those of Comparative Examples 1 to 6. It can be seen that the sodium-electric positive electrode material obtained by the present invention can be used in a high-voltage working environment and can improve the electrical performance of the battery.

[0080] So how do we regulate the relative strength of the crystal planes in the sodium cathode material? We designed Examples 1 to 10 and compared them with Comparative Examples 1 to 6 to verify this.

[0081] Through the preparation method of the present invention, the exposure of the crystal face of the sodium cathode material is mainly controlled by the main factor, and other factors play an auxiliary regulatory role. However, the final exposure trend of the crystal face is mainly due to the regulatory effect of the main factor. During the preparation method of the present invention, the sodium content, oxygen amount, sintering temperature and the main elements in the sodium cathode material play a more important role, which can directly affect the exposure of the (012) crystal face, the (003) crystal face and the (104) crystal face. To this end, we verify this through Examples 1 to 10.

[0082] First, we can find by comparing Examples 1 to 12 with Comparative Examples 1 to 6 that by adjusting the ratio between the sodium cathode material precursor and the sodium source, a sodium-poor sodium cathode material is obtained, and the crystal plane of the sodium-poor sodium cathode material is exposed within the relative strength of the present invention. We believe that this may be because the sodium-poor sodium cathode material structure can increase the occupancy of Cu, Mn, Ni, and Ti in the sodium cathode material structure, thereby obtaining a sodium cathode material having a crystal plane strength within the scope of the present invention.

[0083] We also found that the sodium cathode material structure contains Cu, Ni, Mn, and Ti, and these substances can be evenly dispersed in the structure, thereby preparing for regulating the relative crystal plane strength of the sodium cathode material. By comparing Example 6 with Example 9 and Example 8 with Example 10, it was found that by changing the proportion of Cu, Ni, Mn, and Ti in the structure of the sodium cathode material, the crystal plane exposure of the sodium cathode material can be further improved. When the increase of Cu and Ti is increased and the decrease of Mn and Ni is reduced, the (012) crystal plane exposure can be increased.

[0084] On this basis, 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 in the sodium-ion cathode material. We can find that when comparing Examples 1-3, as the Na content increases, the exposure of the (012) crystal plane decreases. We can verify our results by comparing Examples 4-6 and Examples 8-9.

[0085] On this basis, we further compared Example 1 and Example 10 and found that the exposure of the (012) crystal plane and the (014) crystal plane in the sodium positive electrode material can be mainly adjusted by adjusting the flow rate of oxygen. By comparing Example 7 and Example 10, we found that the exposure of the (003) crystal plane in the sodium positive electrode material can be mainly adjusted by adjusting the sintering temperature. We also further compared Example 1 with Example 4, Example 2 with Example 5, and Example 3 with Example 6 and found that in Examples 4-6, when the temperature and oxygen content increased at the same time, due to the oxygen flow rate, the exposure of the (012) crystal plane and the (014) crystal plane in the sodium positive electrode material was mainly adjusted, and the sintering temperature was mainly adjusted. The exposure of the (003) crystal plane in the sodium positive electrode material, therefore, the relative strength I of the (012) crystal plane and the (003) crystal plane was presented in Examples 4-6. (012) / I (003) In the rising, the relative intensity I of (012) crystal plane and (104) crystal plane (012) / I (104) and the relative intensity I of (104) crystal plane and (003) crystal plane (104) / I (003) In decreasing.

[0086] In summary, the sodium cathode material obtained by the present invention is used in batteries and can have 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 in the scope of protection 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; and the selection is 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 0.04 - 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.

2. A single crystal sodium cathode material according to claim 1, characterized in that: The sodium positive electrode 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 of Li, B, Mg, Al, Si, Ca, Zr, Zn, Ta, Mo, W, La, Sr, and Sb; 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 spectrum of the sodium positive electrode material, the relative intensity I of the (012) crystal plane and the (003) crystal plane is (012) / I (003) The relative intensity of (104) crystal plane and (003) crystal plane is 0.04-0.

44. (104) / I (003) The relative intensity of (012) crystal plane and (104) crystal plane is 0.14-1.

14. (012) / I (104) It is 0.28-0.

38. Further preferably, the sodium cathode material has characteristic diffraction peaks at 16.5°, 33.4°, 35.4°, 36.7°, 41.7°, and 45.1° in an X-ray powder diffraction pattern represented by a diffraction angle 2θ.

3. A single crystal sodium cathode material according to claim 1, characterized in that: The tap density of the sodium positive electrode material is not less than 1.7 g / cm 3 The specific surface area of ​​the sodium cathode material is less than 0.3 m 2 / g.

4. A single crystal sodium cathode material according to claim 1, characterized in that: The crystal morphology of the sodium cathode material is flat.

5. The method for preparing a single crystal sodium cathode material according to any one of claims 1 to 4, characterized in that: The sodium cathode material precursor and the sodium source are sintered at a sintering temperature of 900°C-1100°C for 13h-17h, and the oxygen flow rate is 0.3L / min-0.7L / min, wherein, based on molar mass, the ratio of the stoichiometric ratio of the Na element in the sodium source to the total stoichiometric ratio of the Cu element, Ni element, Mn element, and Ti element in the sodium cathode material precursor is 0.9-0.95:1, thereby obtaining the sodium cathode material of the present invention.

6. The preparation method according to claim 5, characterized in that The sodium-ion battery cathode material precursor is [Ni g Cu h Mn i Ti j Me k O 2+β , where 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, 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; The raw materials of the sodium-ion battery cathode material further include a sodium source.

7. 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.

8. The preparation method according to claim 5, characterized in that The heating rate to reach the sintering temperature is 1.5°C / min-2.5°C / min.

9. A battery or electrochemical device comprising the sodium cathode material according to any one of claims 1 to 4 or the sodium cathode material obtained by the preparation method according to any one of claims 5 to 8.

10. The battery according to claim 9, characterized in that The battery has a capacity retention rate of not less than 85% after 50 cycles at an operating voltage of 2V-4.5V.

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