Layered oxide positive electrode material for sodium electrode

Abstract

The invention provides a sodium ion positive electrode which comprises a sodium electric layered oxide positive electrode material and has a general formula Na [sigma] Ni [x] Cu [y] Fe [z] Mn [s] M [1a] M [2b] O [2] wherein [sigma] is greater than 0.90 and less than or equal to 1.1, x is greater than 0.2 and less than or equal to 0.5, y is greater than 0 and less than or equal to 0.2, z is greater than 0 and less than or equal to 0.4, s is greater than 0 and less than or equal to 0.4, x + y + z + s + a + b is greater than 0.99 and less than or equal to 1.01, a + b is greater than 0.001 and less than or equal to 0.1, a is not equal to 0, b is not equal to 0, y / (a + b) is greater than or equal to 5 and less than or equal According to the invention, doping elements with proper charge radius ratio and proportion balance are designed in the copper-containing O3 sodium-rich nickel-iron-manganese ternary layered oxide in a matching manner, so that the segregation problem of copper in the system material and the influence on the capacity and the rate capability are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more particularly to a sodium-ion layered oxide cathode material obtained by ion adaptation of charge / radius at the atomic level. Background Technology

[0002] In the high-energy-density route for the rapid industrialization of sodium-ion batteries, layered oxide cathodes are widely recognized as one of the most promising material systems for mass production due to their advantages of high theoretical specific capacity, high compaction density, and high compatibility with ternary lithium-ion battery processes. However, on the one hand, the preparation of Ni-Fe-Mn ternary layered oxides often requires higher solid-state reaction temperatures due to the slow interdiffusion of nickel, iron, and manganese sources, resulting in low product density or uneven distribution, which becomes a bottleneck for improving product performance. On the other hand, Ni-Fe-Mn ternary layered oxides are prone to violent phase transitions during high-voltage sodium removal, leading to the initiation of intergranular cracks and irreversible loss of lattice oxygen, severely limiting cycle life and high-voltage stability. Therefore, the industry has adopted methods such as introducing a small amount of Cu... 2+ On the one hand, raw materials such as CuO, as copper sources, can form a low eutectic with nickel-iron-manganese sources in the early stage of sintering, playing a role in assisting sintering, significantly reducing the sintering temperature and promoting the uniform and stable formation of product grains. On the other hand, Cu... 2+ radius and Ni 2+ Matching can reduce the average valence state of the transition metal layer, decrease the lattice shrinkage at the end of sodium removal, and suppress oxygen vacancy generation with stronger Cu-O bonds, thereby improving the lattice stability of Ni-Fe-Mn ternary layered oxides.

[0003] However, Cu 2+ The solid solution limit in Ni-Fe-Mn ternary layered oxides is relatively low, and its diffusion rate at the same temperature is significantly higher than that of Ni. 2+ Fe 3+ Mn 4+ Ions, leading to Cu 2+ Uneven distribution of Cu in the material system leads to 2+ The enrichment of segregated phases, such as CuO / Cu2O, at grain boundaries, twin boundaries, and oxygen vacancies can easily lead to defects and generate significant internal stress. This stress can cause cracking during material cycling due to high internal stress, and also result in poor cycle retention and rate discharge performance. Therefore, controlling copper segregation and the defects it generates during material synthesis to improve the cycle stability and rate performance of the material has become a key technical challenge that urgently needs to be addressed to achieve the large-scale application of high-voltage O3-type sodium-rich layered cathodes.

[0004] Therefore, this application is submitted. Summary of the Invention

[0005] In light of the background technology, this invention provides a sodium-ion layered oxide cathode material based on atomic design. By matching and designing doping elements with suitable charge radius ratios and balancing their proportions in a copper-containing O3-rich sodium-iron-manganese ternary layered oxide, the segregation problem of copper in this system material and its impact on capacity and rate performance are effectively solved.

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention include: Firstly, this invention proposes a sodium-ion layered oxide cathode material with the general formula: Na σ Ni x Cu y Fe z Mn s M1 a M2 b O2, where subscripts represent molar ratios, 0.90<σ≤1.1, 0.2<x≤0.5, 0<y≤0.2, 0<z≤0.4, 0<s≤0.4, 0.99≤x+y+z+s+a+b≤1.01, 0.001<a+b≤0.1, a≠0, b≠0, 5≤y / (a+b)≤15, M1 is one or more elements with a charge radius ratio of 20~30, M2 is one or more elements with a charge radius ratio of 55~70, and the average charge of M1 and M2 is between 2.5 and 3.5.

[0007] In this invention, the charge radius ratio refers to the ratio of the ionic valence charge of an element in a material to its ionic radius (nm). The ionic valence charge and ionic radius of different elements can be obtained by consulting publicly available information, such as the Shannon ionic radius database, using Cu as an example. 2+ For example, its charge radius ratio is the ratio of the ionic valence charge number 2 to the ionic radius 0.073 measured in nanometers, i.e., Cu 2+ The charge radius ratio is 27.4. As some specific examples, the charge radius ratios of the ions formed by some elements are as follows: Mg 2+ , 27.8; Zn 2+ ,27;Ca 2+ ,20;Ti 4+ , 66.1; Zr 4+ 55.6; W 4+ , 61.5; Mo 4+ 61.5; Li + , 13.16; B 3+ , 111.11; La 3+ , 29.07; Al 3+ 56.07; Nb 5+ 78.13; etc., in nm -1 .

[0008] In this invention, the average charge refers to the average charge obtained by calculating the ratio of the sum of the products of the charges of different elements and their stoichiometric coefficients to the sum of the stoichiometric coefficients of these elements. For example, in the above general formula, if the ionic charge of element M1 is m and the ionic charge of element M2 is n, then the average charge of M1 and M2 is (m×a+n×b) / (a+b).

[0009] The sodium-ion layered oxide cathode material represented by the above-mentioned general formula provided by this invention defines a basic material system of copper-containing O3-rich sodium-iron-manganese ternary layered oxides by the formula "0.90<σ≤1.1, 0.2<x≤0.5, 0<y≤0.2, 0<z≤0.4, 0<s≤0.4, 0.99≤x+y+z+s+a+b≤1.01, 0.001<a+b≤0.1". This system has the advantages of high energy density and high initial efficiency. The introduction of copper balances the low-temperature sintering of this material system with the initial lattice stability achieved through deep desodium removal. To further address copper segregation and balance deep discharge at high rates and long-cycle lattice stability, this invention further designs elemental adaptations for different dopants in terms of charge radius ratio. We found that by introducing appropriate amounts of dopants lower than or close to, and limitedly slightly higher than, Cu... 2+ The elements with charge radius ratios of (M1, 20~30) and higher than Cu 2+ The element with a charge radius ratio of (M2, 55~70) is beneficial for forming a solid solution with copper and inhibiting Cu. 2+ On the one hand, it can facilitate ion migration, and on the other hand, it can enhance the bond energy between the dopant element and oxygen atoms, thereby achieving the binding effect of copper at defects or grain boundaries and solving the problem of copper segregation. The introduction amount and ratio of the two types of elements M1 and M2 are closely related to the copper content. Therefore, 5≤y / (a+b)≤15 reflects the compatibility between the introduction amount of the two and the copper content. The design of the average charge between 2.5 and 3.5 not only balances the mutual ratio relationship of the two types of elements M1 and M2, and balances the dual effects of solid solution and bond energy, but the control of this average charge range is also compatible with the equilibrium valence state of the Ni-Fe-Mn ternary solid solution layer structure, which is conducive to stabilizing the layer structure framework, further improving the structural stability under high pressure, and also bringing greater advantages to the long-cycle performance of deep Na lower limit insertion and extraction under sodium-rich capacity.

[0010] In some preferred embodiments, the general formula Na σ Ni x Cu y Fe z Mn s M1 a M2 bIn O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15. M1 is one or more elements with a charge radius ratio of 20 to 30, and M2 is one or more elements with a charge radius ratio of 55 to 70. The average charge of M1 and M2 is between 2.5 and 3.5. Optimizing the copper content enhances its advantages in O3-rich sodium-type nickel-iron-manganese ternary layered oxides and minimizes the impact on segregation by maintaining its intrinsic content.

[0011] In some preferred embodiments, the general formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b In O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15. M1 is one or more elements with a charge radius ratio of 25 to 29, and M2 is one or more elements with a charge radius ratio of 55 to 70. The average charge of M1 and M2 is between 2.5 and 3.5. We found it to be closer to Cu. 2+ The ratio of the charge radius of M1 in stable Cu 2+ It has a greater advantage in this regard.

[0012] In some preferred embodiments, the general formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b In O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15. M1 is one or more elements with a charge radius ratio of 25 to 29, and M2 is one or more elements with a charge radius ratio of 55 to 70. The average charge of M1 and M2 is between 2.7 and 3.3. The optimized average charge in equilibrium Cu... 2+Solid solution treatment is beneficial for further improving the stability of the Ni-Fe-Mn ternary architecture and enhancing the material's long-cycle capability under high pressure.

[0013] In some preferred embodiments, the general formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b In O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15, M1 is one or more elements with a charge radius ratio of 25 to 29, M2 is selected from at least one element M21 with a charge radius ratio of 55 to 60 and at least one element M21 with a charge radius ratio of 61 to 70, and the average charge of M1, M21, and M22 is between 2.7 and 3.3.

[0014] In some preferred embodiments, the general formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b In O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15, M1 is one or more elements with a charge radius ratio of 25 to 29, M2 is selected from at least one element M21 with a charge radius ratio of 55 to 60 and at least one element M21 with a charge radius ratio of 61 to 70, and the difference between the charge radius ratios of elements M21 and M22 is 4 to 7, and the average charge of M1 and M21, M22 is between 2.7 and 3.3.

[0015] We discovered that, based on satisfying the charge radius ratio and average charge of M1 and M2, further selection of two M2 elements with different charge radius ratio levels enabled fine-tuning of the element design, compared to Cu. 2+ Elements with a higher charge radius ratio are solution-fitted at an optimized level, avoiding the localized minor distortions that may result from transitions with larger charge radii, thereby achieving a further breakthrough in rate performance.

[0016] In some preferred embodiments, M1 is selected from elements with ionic valence charge numbers of +2 to +3, including magnesium (Mg), zinc (Zn), calcium (Ca), lanthanum (La), etc.; M2 is selected from elements with ionic valence charge numbers of +4 to +6, including titanium (Ti), zirconium (Zr), tungsten (W), molybdenum (Mo), niobium (Nb), etc.

[0017] The materials described above in this invention can be prepared using common preparation methods, and this invention does not limit the methods used. For example, solid-state sintering can be used. Exemplarily, nickel source, manganese source, iron source, copper source, dopant source, and sodium source can be thoroughly mixed according to the target stoichiometric coefficients and then sintered to obtain the material.

[0018] In some schemes, the nickel source, manganese source, iron source, copper source, and doping source can be oxides, hydroxides, carbonates, or organic acid salts (such as oxalates) of these elements. For example, the nickel source includes one or more of NiO, Ni(OH)2, NiCO3, and NiC2O4; the manganese source includes one or more of MnO, Mn2O3, Mn3O4, MnO2, MnCO3, and MnC2O4; the iron source includes one or more of Fe2O3, Fe(OH)3, FeCO3, and FeC2O4; the copper source includes one or more of CuO, Cu(OH)2, and CuCO3·Cu(OH)2; and the sodium source includes one or more of sodium carbonate and sodium bicarbonate.

[0019] In some schemes, in order to optimize reaction kinetics, promote element diffusion and low-temperature sintering reaction, improve reaction efficiency, and improve particle size distribution, the initial particle size of each raw material can be optimized. Nickel, manganese, iron, copper and doping sources with D50≤20μm are used, and sodium source with 4μm≤D50≤10μm is used.

[0020] In some schemes, solid-state sintering is carried out in an air or oxygen atmosphere.

[0021] In some designs, the sintering temperature is between 700 and 1050°C.

[0022] In some schemes, the total sintering time is between 10 and 20 hours.

[0023] In some schemes, the sintering process can be performed once or multiple times, with low-temperature sintering followed by high-temperature sintering being preferred. For example, a first sintering at 700~850℃ for 5-10 hours is performed, followed by a second sintering at 900~1050℃ for 5-15 hours.

[0024] In some schemes, after sintering, the sintered material can be crushed and screened to obtain sodium-ion layered oxide cathode material products that meet the target particle size range.

[0025] The sodium-ion layered oxide cathode material obtained by this invention can have a particle size distribution of 4μm≤D50≤8μm.

[0026] The sodium-ion layered oxide cathode material obtained by this invention did not exhibit a mirror-symmetric structure in SEM after 200 cycles at 45°C and 1C.

[0027] Secondly, the present invention also provides a sodium-ion positive electrode sheet, comprising the above-mentioned sodium-ion layered oxide positive electrode material and a current collector. The choice of current collector is not limited, but aluminum foil is preferred.

[0028] Thirdly, the present invention also provides a battery comprising the aforementioned sodium-ion positive electrode, and further comprising a negative electrode, a separator, and an electrolyte. The selection of the negative electrode, separator, and electrolyte is not limited, and can be chosen and applied from common materials used in sodium-ion batteries.

[0029] Fourth, the present invention provides an electrical device including the aforementioned battery. Exemplary examples include, but are not limited to, 3C digital devices (mobile phones, tablets, laptops, Bluetooth headsets, cameras, smartwatches), small household appliances (robot vacuum cleaners, projectors), power tools (electric drills, chainsaws, garden shears), personal transportation (electric bicycles, electric skateboards, balance bikes, electric motorcycles), low-speed vehicles (three-wheeled delivery vehicles, four-wheeled mobility scooters for the elderly, sightseeing vehicles), special-purpose vehicles (electric forklifts, AGVs, airport shuttle buses, electric ships), energy storage scenarios (home energy storage cabinets, industrial and commercial energy storage cabinets, communication base station UPS, data center backup power, wind-solar hybrid street light energy storage), grid-level applications (energy storage containers, peak-shaving and frequency-regulating power stations), and military and outdoor applications (drones, robots, portable power supplies, field energy storage boxes), etc.

[0030] Through the above technical solution, this invention, by designing materials at the atomic level, matches and designs doping elements with suitable charge-radius ratios in a copper-containing O3-rich sodium-type nickel-iron-manganese ternary layered oxide, and optimizes their ratio, achieving the doping effect of Cu in the Ni-Fe-Mn ternary layered framework structure. 2+ Centered on the charge-radius fit, this system retains the advantages of high energy density and low-temperature sintering while solving the problems of copper segregation and instability at high rates and long cycles, resulting in a material particle size distribution that is skewed towards smaller sizes. Furthermore, the charge-radius ratio and average charge of the introduced dopant elements are deeply optimized to improve the charge fit, solid solution bond energy, and stabilizing effect on the ternary architecture of the material's microstructure, achieving further optimization and improvement of the material's long-cycle performance under high pressure and high rates. Attached Figure Description

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

[0032] Figure 1 The image shows the SEM image of the material in Example 1 before the cyclic testing.

[0033] Figure 2 The image shows the SEM image of the material in Example 1 after cyclic testing.

[0034] Figure 3 The image shows the SEM image of the material in Comparative Example 6 before the cyclic testing.

[0035] Figure 4 The image shows the SEM image of the material in Comparative Example 6 after cyclic testing.

[0036] Figure 5 The image shows the XRD pattern of the material in Example 4.

[0037] Figure 6 The image shows the XRD pattern of the material in Comparative Example 6. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0039] All chemical raw materials used in the following examples and comparative examples were commercially available, and all apparatuses and operations involved were conventional in the art. All testing methods involved were conventional in the art.

[0040] Example 1: Preparation of layered oxide Na 1.02 Ni 0.2985 Cu 0.06965 Fe 0.20895 Mn 0.4179 Mg 0.0025 Zr 0.0025O2 was used to weigh out 13.91g of Ni(OH)2, 17.81g of NiCO3, 31.87g of Mn3O4, 16.68g of Fe2O3, 7.70g of basic copper carbonate, 54.05g of sodium carbonate, 0.10g of MgO, and 0.31g of ZrO2 according to the stoichiometric ratio of the chemical formula. The above raw materials were mixed, sand-milled and spray-dried, and then sintered in air at a heating rate of 2.0℃ / h for 700℃ / 5h and 960℃ / 15h to obtain sintered material. The material was then coarsely crushed, finely crushed and sieved to obtain the product.

[0041] Example 2: Using the same method as in Example 1, layered oxide Na was prepared according to different stoichiometric ratios. 1.0 2Ni 0.297 Cu 0.0693 Fe 0.2079 Mn 0.4158 Mg 0.005 Zr 0.005 O2.

[0042] Example 3: Using the same method as in Example 1, layered oxide Na was prepared according to different stoichiometric ratios. 1.0 2Ni 0.2982 Cu 0.06958 Fe 0.20874 Mn 0.41748 Mg 0.0015 Zn 0.0015 Zr 0.003 O2.

[0043] Example 4: Using the same method as in Example 1, layered oxide Na was prepared according to different stoichiometric ratios. 1.0 2Ni 0.2976 Cu 0.06944 Fe 0.20832 Mn 0.41664 Mg 0.002 Zn 0.002 Zr 0.002 Ti 0.002 O2.

[0044] Example 5: Using the same method as in Example 1, layered oxide Na was prepared according to different stoichiometric ratios. 1.0 2Ni 0.2976 Cu 0.06944 Fe 0.20832 Mn 0.41664 Mg 0.002 Ca 0.002 Zr 0.002 Ti 0.002 O2.

[0045] Example 6: Using the same method as in Example 1, layered oxide Na was prepared according to different stoichiometric ratios. 1.0 2Ni 0.2982 Cu 0.06958 Fe 0.20874 Mn 0.41748 Mg 0.003 Zr 0.0015 W 0.0015 O2.

[0046] Example 7: Using the same method as in Example 1, layered oxide Na was prepared according to different stoichiometric ratios. 1.0 2Ni 0.2982 Cu 0.06958 Fe 0.20874 Mn 0.41748 Mg 0.003 Zr 0.003 O2.

[0047] Comparative Example 1: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.0 2Ni 0.2985 Cu 0.06965 Fe 0.20895 Mn 0.4179 Mg 0.005 O2.

[0048] Comparative Example 2: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.0 2Ni 0.2985 Cu 0.06965 Fe 0.20895 Mn 0.4179 Zr 0.005 O2.

[0049] Comparative Example 3: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.0 2Ni 0.2982 Cu 0.06958 Fe 0.20874 Mn 0.41748 Mg 0.003 Zn 0.003 O2.

[0050] Comparative Example 4: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.0 2Ni 0.2988 Cu 0.06972 Fe 0.20916 Mn 0.41832 Zr 0.002 Ti 0.002 O2.

[0051] Comparative Example 5: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.0 2Ni 0.2985 Cu 0.06965 Fe 0.20895 Mn 0.4179 Mg 0.004 Zr 0.001 O2.

[0052] Comparative Example 6: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.02 Ni 0.3 Cu 0.07 Fe 0.21 Mn 0.42 O2.

[0053] Comparative Example 7: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.0 2Ni 0.225 Fe 0.345 Mn 0.3525 Cu 0.055 Zn 0.02 Ca 0.015 B 0.005 Li 0.005 O2.

[0054] Comparative Example 8: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.0 2Ni 0.20 Fe 0.345 Mn 0.35 Cu 0.055 Zn 0.02 Ca 0.015 La 0.005 Ti 0.005 O2.

[0055] Comparative Example 9: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 0.6 6Ni 0.18 Mn 0.57 Zn 0.05 Cu 0.05 Mg 0.05 Ti 0.1 O2.

[0056] Comparative Example 10: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 0.66 Ni 0.18 Mn 0.57 Zn 0.05 Cu 0.05 Mg 0.05 Al0.05 Nb 0.05 O2.

[0057] Comparative Example 11: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 0.95 Ni 0.241098 Fe 0.37092 Mn 0.27819 Cu 0.048546 Zn 0.048546 Mg 0.0081 Ti 0.0046 O2.

[0058] Comparative Example 12: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.02 Cu 0.12 Mn 0.39 Ni 0.29 Fe 0.2 Mg 0.05 Ca 0.03 Ti 0.03 O2.

[0059] Comparative Example 13: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 0.8 Ni 2+ 0.16 Ni 3+ 0.06 Fe 0.22 Mn 0.44 Cu 0.05 Mg 0.05 Zr 0.01 Ti 0.01 O2.

[0060] Comparative Example 14: Layered oxide Na was prepared using the same method as in Example 1, but with different stoichiometric ratios. 1.04 Cu 0.12 Mn 0.39 Fe 0.26 Mg 0.0002 Ti 0.0034 Zr 0.0031 Ni 0.40 O 2.22 .

[0061] In the above embodiments and comparative examples, the sources of the doping elements can all be their conventional oxides, hydroxides, or carbonates. For example, Zn source can be ZnO, Ti source can be TiO2, Ca source can be CaCO3, W source can be WO3, B source can be B2O3, Li source can be Li2O, La source can be La2O3, Al source can be Al2O3, Nb source can be Nb2O5, etc.

[0062] The positive electrode materials prepared in the above embodiments and comparative examples were used as active materials. They were mixed at a mass ratio of active material:SP:PVDF of 90:5:5, and NMP was added to prepare a viscous adhesive. This adhesive was then coated onto aluminum foil and baked in a vacuum drying oven at 120°C for 12 hours to obtain the positive electrode sheet. Using a sodium metal sheet as the counter electrode, glass fiber (Waterman) as the separator, and 1 mol / L NaPF6 EC / DMC = 1:1 (Alfa) as the electrolyte, 2032 coin cells were assembled in an Ar protective glove box. The cells were tested within a voltage range of 2.5~4.0V, cyclically at 0.1C for 3 weeks, and at 45°C for 200 cycles at 1C. The charge / discharge specific capacity of each cell in the first cycle at 0.1C, and the discharge retention rate after the first and 200 cycles at 1C were recorded. CuO segregation in the positive electrode material was detected by XRD, and the proportion of segregated impurities could be calculated from the peak area. The layered oxide cathode materials prepared in Example 1 and Comparative Example 6 were cross-sectioned using an argon-ion polishing instrument, and SEM images were analyzed at an accelerating voltage of 15 kV and a magnification of ~10 kV to examine elemental segregation, defects, and cracks within the electrode sheets. The test results for each material are listed in Table 1 and... Figures 1-6 middle.

[0063] Table 1

[0064] Based on the above embodiments and comparative examples, it can be seen that the material design of the present invention can solve the problem of copper segregation in copper-containing O3-rich sodium-type nickel-iron-manganese ternary layered oxides. No CuO impurity peak was detected by XRD in any of the embodiments, the D50 of the material can reach below 7.5 μm, the first-cycle discharge at 1C reaches more than 130 mAh / g, and the discharge retention rate at 45℃ from 1C to 200 cycles reaches more than 97%.

[0065] At the same time Figures 1-6 It can be seen that, under CP-SEM backscattered electron mode, the material of Example 1 before and after cycling ( Figure 1-2 The particle boundaries were distinct, and no CuO segregation or particle fusion was found in any of them, whereas the material in Comparative Example 6 showed no such phenomenon before cycling. Figure 3 Although it has a dispersed particle state, after 200 cycles at 45°C (1°F), Figure 4 Due to the significant segregation of CuO at the particle boundaries, a significant fusion phenomenon occurs between the particles, resulting in a mirror-symmetric structure and an overall increase in particle size. Figure 5-6 The XRD results of Example 4 and Comparative Example 6 clearly show that a significant CuO segregation peak appears in Comparative Example 6, while no CuO segregation peak is observed in Example 4.

[0066] It is evident that the present invention effectively suppresses CuO segregation based on charge-radius adaptation at the atomic level, thereby reducing the overall particle size of D50 and improving the long-cycle capability of the material at high temperatures and rates.

[0067] As can be seen from Examples 1-7 compared to Comparative Examples 1-4, neither adapting M1-type doping elements alone nor adapting M2-type doping elements alone can achieve a good effect in suppressing Cu segregation. Although individual doping has a limited effect on improving the initial efficiency, it is difficult to effectively improve the particle distribution, rate performance, and structural stability over long cycles.

[0068] Examples 1-7 further demonstrate the advantages of the present invention based on element design adaptation relationships compared to Comparative Examples 7-14. For instance, Comparative Example 7 introduces elements B with significantly different charge radii (B0, B1, B2, B3, B4, B5, B6, B7, B< 3+ The charge radius ratio is 111.11 nm. -1 ) and Li (Li + The charge radius ratio is 13.16 nm. -1 Its rate performance deteriorates significantly. For example, the relatively high Cu content in Comparative Examples 8, 12, and 14... 2+ The relatively low content of doping elements makes it difficult to achieve sufficient solid solution and bond energy optimization, and the charge balance cannot be well configured, thus failing to effectively solve the copper segregation problem. As shown in Comparative Example 11, in the sodium-rich system, even with relatively low Cu content, the segregation of copper is difficult to achieve. 2+ Even with relatively high dopant content, effective improvements in segregation and rate performance cannot be achieved under unsuitable charge radius ratios and average charges. As shown in Comparative Examples 9, 10, and 13, although certain combinations of charge radius ratios and average charges reduce the occurrence of segregation, these phenomena are more prevalent in sodium-poor O3 structural systems. Not only is the rate improvement limited, but the inherent limitations of the sodium-poor structure also lead to an inevitable shift in particle size distribution towards larger particles due to the inherent instability of the framework structure.

[0069] Examples 1-7 further verified the stabilizing effect of the average charge of M1 and M2 on the sodium-rich layered oxide of O3 compared with Comparative Example 5. Although M1 and M2 were configured in terms of charge radius ratio, the excessively high difference in average charge failed to fully eliminate the segregation of CuO. Although the rate capability was significantly improved to a certain extent compared with other comparative examples, the improvement was limited.

[0070] In each embodiment, a comparison between Embodiment 4 and Embodiment 5 shows that Zn 2+ Having relative to Ca 2+ Closer to Cu 2+ The charge radius ratio, in Example 4, is closer to Cu. 2+ The M1 (25~29) with a charge radius ratio exhibits better performance advantages.

[0071] In each embodiment, a comparison between Embodiment 6 and Embodiment 7 shows that the M2 element is selected from Zr with a charge radius ratio of 55-60. 4+ W with a charge radius ratio of 61~70 4+ Combining them, compared to using Zr alone 4+ It exhibits better particle size distribution and rate performance tendency, confirming the further advantages of hierarchical optimization of M2 for performance improvement.

[0072] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

Claims

1. A sodium electro-layered oxide cathode material having the general formula: Na σ Ni x Cu y Fe z Mn s M1 a M2 b O2, wherein, The lower subscript represents a molar ratio, 0.90 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0 < y ≤ 0.2, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x+y+z+s+a+b ≤ 1.01, 0.001 < a+b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a+b) ≤ 15, M1 is one or more of elements with a charge radius ratio of 20-30, M2 is one or more of elements with a charge radius ratio of 55-70, and the average charge of M1 and M2 is between 2.5-3.

5.

2. The sodium electro-layered oxide cathode material of claim 1, wherein, General formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15, M1 is one or more of elements with a charge radius ratio of 20 to 30, M2 is one or more of elements with a charge radius ratio of 55 to 70, and the average charge of M1 and M2 is between 2.5 and 3.

5.

3. The sodium electro-layered oxide cathode material of claim 1, wherein, General formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15, M1 is one or more of elements with a charge radius ratio of 25 to 29, M2 is one or more of elements with a charge radius ratio of 55 to 70, and the average charge of M1 and M2 is between 2.5 and 3.

5.

4. The sodium electro-layered oxide cathode material of claim 1, wherein, Na σ Ni x Cu y Fe z Mn s M1 a M2 b O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15, M1 is one or more of elements having a charge radius ratio of 25 to 29, M2 is one or more of elements having a charge radius ratio of 55 to 70, and the average charge of M1 and M2 is between 2.7 and 3.

3.

5. The sodium electro-layered oxide cathode material of claim 1, wherein, General formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15, M1 is one or more of elements with a charge radius ratio of 25 to 29, M2 is selected from at least one of elements M21 with a charge radius ratio of 55 to 60 and at least one of elements M21 with a charge radius ratio of 61 to 70, and the average charge of M1 and M21, M22 is between 2.7 and 3.

3.

6. The sodium electro-layered oxide cathode material of claim 1, wherein, General formula Na σ Ni x Cu y Fe z Mn s M1 a M2 b O2, 1.0 < σ ≤ 1.1, 0.2 < x ≤ 0.5, 0.03 < y ≤ 0.09, 0 < z ≤ 0.4, 0 < s ≤ 0.4, 0.99 ≤ x + y + z + s + a + b ≤ 1.01, 0.001 < a + b ≤ 0.1, a ≠ 0, b ≠ 0, 5 ≤ y / (a + b) ≤ 15, M1 is one or more of elements with a charge radius ratio of 25-29, M2 is selected from at least one of elements M21 with a charge radius ratio of 55-60 and at least one of elements M21 with a charge radius ratio of 61-70, the difference between the charge radius ratios of the two elements M21 and M22 is 4-7, and the average charge of M1 and M21, M22 is between 2.7 and 3.

3.

7. The sodium electro-layered oxide cathode material of claim 1, wherein, M1 is selected from elements with an ionic valence charge number of +2 to +3, including one or more of magnesium (Mg), zinc (Zn), calcium (Ca), lanthanum (La); M2 is selected from elements with an ionic valence charge number of +4 to +6, including one or more of titanium (Ti), zirconium (Zr), tungsten (W), molybdenum (Mo), niobium (Nb).

8. The sodium electro-layered oxide cathode material of claim 1, wherein, The sodium battery layered oxide positive electrode material satisfies at least one of the following performance indicators: (1) a particle size distribution of 4 μm ≤ D50 ≤ 8 μm; (2) after 1C cycling at 45°C high temperature for 200 cycles, no mirror symmetry structure appears in SEM.

9. A method for preparing the sodium battery layered oxide positive electrode material of any one of claims 1-8, wherein a nickel source, a manganese source, an iron source, a copper source, a doping source, and a sodium source are mixed according to a target stoichiometric coefficient, and then sintered to obtain the sodium battery layered oxide positive electrode material. Preferably, the nickel source, the manganese source, the iron source, the copper source, and the doping source are oxides, hydroxides, carbonates, or organic acid salts of these elements. Preferably, the nickel source, the manganese source, the iron source, the copper source, and the doping source have a D50 ≤ 20 μm, and the sodium source has a D50 of 4 μm ≤ D50 ≤ 10 μm. Preferably, the solid-phase sintering is performed in air or an oxygen atmosphere. Preferably, the sintering temperature is between 700-1050°C. Preferably, the total sintering time is between 10-20h. Preferably, the sintering is performed one or more times. Preferably, the sintering process comprises performing a first sintering at 700-850°C for 5-10h, and then performing a second sintering at 900-1050°C for 5-15h. Preferably, after the sintering is completed, the sintered material is crushed and sieved to obtain the sodium battery layered oxide positive electrode material product.

10. A sodium ion positive electrode sheet, a battery, or an electrical device, comprising the sodium battery layered oxide positive electrode material of any one of claims 1-8.

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