Layered oxide positive electrode material, method for its preparation, positive electrode composition, sodium-ion secondary battery and use

Abstract

The application discloses a layered oxide positive electrode material, a preparation method thereof, a positive electrode composition, a sodium-ion secondary battery and an application. A general formula of the layered oxide positive electrode material is Na x Cu a Ni b Fe c Mn d M y O 2+nδ , wherein each parameter in the general formula has a range defined in the specification, and wherein the doping element M at least includes Mg+Al+Ti. The application can effectively eliminate CuO impurities in the product, improve the electrochemical performance of the corresponding sodium-ion secondary battery, such as the initial efficiency of the battery.

Description

[0001] This application is a divisional application of Chinese invention patent application filed on May 5, 2023, with application number 202310490958.2 and entitled "Layered oxide cathode material, preparation method thereof, cathode composition, sodium-ion secondary battery and use thereof". Technical Field

[0002] This invention relates generally to the field of energy storage technology, particularly to the field of sodium-ion secondary batteries. Specifically, this invention relates to layered oxide cathode materials, their preparation methods, cathode compositions comprising the same, sodium-ion secondary batteries comprising the cathode compositions, and the uses of the sodium-ion secondary batteries. Background Technology

[0003] Lithium-ion rechargeable batteries are widely used in portable electronic devices and electric vehicles due to their high energy density and long cycle life. However, the scarcity and uneven distribution of lithium resources, especially with the explosive growth of the electric vehicle industry in recent years, have led to a continuous rise in upstream material prices, posing a significant challenge to the application of lithium-ion rechargeable batteries. Compared to lithium, sodium is abundant and inexpensive, thus attracting increasing attention.

[0004] Compared to lithium-ion batteries, sodium-ion batteries have a lower energy density. Although studies have shown that layered oxide cathode materials have a high theoretical capacity and therefore a high energy density, their inherent air stability is poor, leading to inconsistent physical and electrochemical properties in the finished product. Extensive research has revealed that introducing Cu into layered oxide cathode materials can improve air stability. However, adding Cu, especially at high Cu content, results in the formation of a large amount of CuO impurities in the layered oxide cathode material, deteriorating the electrochemical performance of sodium-ion batteries, such as reducing the first-cycle efficiency. Existing technologies typically employ methods to reduce CuO impurities, including increasing sintering temperature, extending sintering time, optimizing the sintering atmosphere, and reducing the proportion of impurity raw materials. However, these methods all negatively impact material performance, and the improvement in electrochemical performance obtained by reducing the proportion of impurity raw materials is not significant or does not meet the modification requirements.

[0005] In view of the above problems, technicians urgently need to develop a new layered oxide cathode material that contains a high Cu content and has less CuO impurities. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a new layered oxide cathode material and its related sodium-ion secondary battery, which aims to eliminate the CuO impurity phase in the layered oxide cathode material and effectively improve the electrochemical performance of the sodium-ion secondary battery, such as the first-time efficiency of the coin cell.

[0007] In a first aspect, the present invention relates to a layered oxide cathode material having the following general formula:

[0008] Na x Cu a Ni b Fe c Mn d M y O 2+nδ ,

[0009] Where 0.60≤x≤1.20, 0.05≤a≤0.40, 0.03≤b≤0.70, 0.10≤c≤0.45, 0.10≤d≤0.45, 0<y≤0.30, and satisfying x+2a+2b+3c+3d+2y<4<x+2a+3b+3c+4d+4y, 0.95≤a+b+c+d+y≤1.05, 0<n≤0.1, -1≤δ≤3; and

[0010] M includes Mg+Al+Ti, and optionally includes one or more of Ca, B, Li, K, W, Mo, Sr, Y, Sn, Sb, and Ce.

[0011] In a second aspect, the present invention relates to a method for preparing a layered oxide cathode material according to the first aspect of the present invention, comprising the following steps:

[0012] Step a: Mix Na source, Cu source, Ni source, Fe source, Mn source and M source uniformly in stoichiometric ratio to obtain a mixed precursor;

[0013] Step b: Sinter the precursor obtained in step a; and

[0014] Step c: Cool the product obtained in step b, and optionally crush and sieve it.

[0015] In a third aspect, the present invention relates to a cathode composition comprising the layered oxide cathode material according to the first aspect of the present invention.

[0016] In a fourth aspect, the present invention relates to a sodium-ion secondary battery comprising the positive electrode composition described in the third aspect of the invention.

[0017] In a fifth aspect, the present invention relates to the use of the sodium-ion secondary battery of the fourth aspect of the present invention in energy storage devices for solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies or communication base stations.

[0018] This invention utilizes Mg, Al, and Ti as doping elements to effectively eliminate the CuO impurity phase in layered oxides, ultimately improving the electrochemical performance of the corresponding sodium-ion secondary batteries, such as the first-efficiency coin cell. Compared to existing technologies, this invention has a higher proportion of impurity raw materials, effectively improving the performance of layered oxide cathode materials. Furthermore, this invention enables the production of near-pure layered oxide cathode materials with a high Cu content (below 0.3 molar Cu content) without increasing the sintering temperature and time.

[0019] Specifically, the present invention is achieved by the following:

[0020] 1. A layered oxide cathode material having the following general formula:

[0021] Na x Cu a Ni b Fe c Mn d M y O 2+nδ ,

[0022] Where 0.60≤x≤1.20, 0.05≤a≤0.40, 0.03≤b≤0.70, 0.10≤c≤0.45, 0.10≤d≤0.45, 0<y≤0.30, and satisfying x+2a+2b+3c+3d+2y<4<x+2a+3b+3c+4d+4y, 0.95≤a+b+c+d+y≤1.05, 0<n≤0.1, -1≤δ≤3; and

[0023] M is Mg+Al+Ti+Li.

[0024] 2. The layered oxide cathode material according to item 1, wherein M further comprises one or more of Ca, B, Li, K, W, Mo, Sr, Y, Sn, Sb, and Ce.

[0025] 3. The layered oxide cathode material according to item 1 or 2, wherein 0.70 ≤ x ≤ 1.20.

[0026] 4. The layered oxide cathode material according to item 1 or 2, wherein 0.05 ≤ a ≤ 0.30.

[0027] 5. The layered oxide cathode material according to item 1 or 2, wherein 0.03 ≤ b ≤ 0.60.

[0028] 6. The layered oxide cathode material according to item 1 or 2, wherein 0.04 ≤ y ≤ 0.20.

[0029] 7. The layered oxide cathode material according to item 1 or 2, wherein the molar ratio of Al / Mg is from 1:3.50 to 1:0.25, and the molar ratio of Ti / Mg is from 1:6.00 to 1:0.05.

[0030] 8. The layered oxide cathode material according to item 1 or 2, wherein the molar ratio of Al / Mg is from 1:3.00 to 1:0.25.

[0031] 9. The layered oxide cathode material according to item 1 or 2, wherein the molar ratio of Ti / Mg is from 1:5.00 to 1:0.05.

[0032] 10. The layered oxide cathode material according to item 1 or 2, wherein y / a ranges from 1:9.00 to 1:0.10.

[0033] 11. The layered oxide cathode material according to item 10, wherein y / a ranges from 1:7.50 to 1:0.25.

[0034] 12. The layered oxide cathode material according to item 1 or 2, wherein the molar ratio of Mg / Cu is from 1:40 to 1:1.00; and / or

[0035] The molar ratio of Al / Cu is 1:30 to 1:1.50; and / or

[0036] The molar ratio of Ti / Cu is from 1:40 to 1:0.25.

[0037] 13. The layered oxide cathode material according to item 12, wherein the molar ratio of Mg / Cu is from 1:30 to 1:2.00.

[0038] 14. The layered oxide cathode material according to item 12, wherein the molar ratio of Al / Cu is from 1:20 to 1:3.50.

[0039] 15. The layered oxide cathode material according to item 12, wherein the molar ratio of Ti / Cu is from 1:30 to 1:0.25.

[0040] 16. The layered oxide cathode material according to item 1 or 2, wherein M is any one of Mg+Al+Ti, or Mg+Al+Ti+Li, or Mg+Al+Ti+K, or Mg+Al+Ti+Sn.

[0041] 17. The layered oxide cathode material according to item 1 or 2, wherein nδ = -0.02 to 0.02.

[0042] 18. The layered oxide cathode material according to item 17, wherein nδ = 0.

[0043] 19. The layered oxide cathode material according to item 1 or 2, wherein the layered oxide cathode material has an O3-type crystal structure.

[0044] 20. A method for preparing a layered oxide cathode material according to any one of items 1 to 19, comprising the following steps:

[0045] Step a: Mix Na source, Cu source, Ni source, Fe source, Mn source and M source uniformly in stoichiometric ratio to obtain a mixed precursor;

[0046] Step b: Sinter the precursor obtained in step a; and

[0047] Step c: Cool the product obtained in step b.

[0048] 21. The method according to item 20, wherein step c further includes crushing and sieving after cooling.

[0049] 22. The method according to item 20 or 21, wherein

[0050] The Na source is one or more compounds selected from the following: sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, sodium oxalate, sodium hydroxide, and sodium oxide;

[0051] The Cu source is one or more compounds selected from the following: copper carbonate, copper nitrate, copper acetate, copper oxalate, copper hydroxide, and copper oxide;

[0052] The Ni source is one or more compounds selected from the following: nickel carbonate, nickel nitrate, nickel acetate, nickel oxalate, nickel hydroxide, and nickel oxide;

[0053] The Fe source is one or more compounds selected from the following: iron carbonate, iron nitrate, iron acetate, iron oxalate, iron hydroxide, and iron oxide;

[0054] The Mn source is one or more compounds selected from the following: manganese carbonate, manganese nitrate, manganese acetate, manganese oxalate, manganese hydroxide, and manganese oxide; and

[0055] The M source is one or more compounds selected from the following forms: carbonates, nitrates, acetates, oxalates, hydroxides, and oxides.

[0056] 23. The method according to item 20 or 21, wherein the mixing in step a is carried out by dry mixing or wet mixing.

[0057] 24. The method according to item 23, wherein the wet mixing is by means of a sol-gel method or a co-precipitation method.

[0058] 25. The method according to item 20 or 21, wherein the sintering in step b is carried out in an oxidizing atmosphere.

[0059] 26. The method according to item 25, wherein the oxidizing atmosphere is compressed air or oxygen.

[0060] 27. The method according to item 20 or 21, wherein the sintering temperature in step b is 700 to 1200°C and the sintering time is 8 to 36 hours.

[0061] 28. The method according to item 27, wherein the sintering temperature in step b is 800 to 1100°C.

[0062] 29. The method according to item 27, wherein the sintering time in step b is 12 h to 20 h.

[0063] 30. A positive electrode composition for use in sodium-ion secondary batteries, comprising the layered oxide positive electrode material according to any one of entries 1 to 19.

[0064] 31. A sodium-ion secondary battery comprising the positive electrode composition according to item 30.

[0065] 32. Use of sodium-ion secondary batteries as described in item 31 in energy storage devices for solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies or communication base stations. Attached Figure Description

[0066] To more clearly illustrate the technical solution of the present invention, the accompanying drawings required for describing the embodiments will be briefly described below. It should be understood that these drawings are only for the purpose of facilitating a better understanding of the present invention by those skilled in the art, and are not intended to limit the scope of the present invention.

[0067] Figure 1 The XRD patterns of the layered oxide cathode materials prepared in Comparative Examples C1-C5 and Examples E1-E10 are shown. Detailed Implementation

[0068] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, this application will be described in detail below. It should be noted that the various aspects, features, embodiments, and advantages described in this application can be compatible and / or combined together.

[0069] Unless otherwise specified, the technical terms used in this specification have the same meaning as commonly understood by those skilled in the art.

[0070] This invention relates to layered oxide cathode materials, methods for preparing the same, cathode compositions comprising the same, sodium-ion secondary batteries comprising the cathode compositions, and uses of the sodium-ion secondary batteries.

[0071] The present invention will be described in detail below.

[0072] Layered oxide positive material

[0073] A first aspect of the present invention provides a layered oxide cathode material having the following general formula:

[0074] Na x Cu a Ni b Fe c Mn d M y O 2+nδ ,

[0075] Where 0.60≤x≤1.20, 0.05≤a≤0.40, 0.03≤b≤0.70, 0.10≤c≤0.45, 0.10≤d≤0.45, 0<y≤0.30, and satisfying x+2a+2b+3c+3d+2y<4<x+2a+3b+3c+4d+4y, 0.95≤a+b+c+d+y≤1.05, 0<n≤0.1, -1≤δ≤3; and

[0076] M includes Mg+Al+Ti, and optionally includes one or more of Ca, B, Li, K, W, Mo, Sr, Y, Sn, Sb, and Ce.

[0077] In layered oxide cathode materials, the presence of CuO impurities degrades the electrochemical performance of corresponding sodium-ion secondary batteries, such as the first-efficiency coin cell. Therefore, the presence of CuO impurities hinders researchers from increasing the Cu doping level, because although adding a certain amount of Cu can improve air stability, it severely degrades performance such as the first-efficiency coin cell. To eliminate CuO impurities, existing technologies typically employ measures such as increasing sintering temperature, extending sintering time, and reducing the Cu content. However, these measures either adversely affect the performance of the resulting cathode material or fail to achieve the desired doping effect due to excessively low doping element content. Compared to existing technologies, this invention, with a high Cu content, simultaneously uses Mg, Al, and Ti as doping elements, effectively eliminating the CuO impurities in layered oxides and improving the electrochemical performance of corresponding sodium-ion secondary batteries, such as the first-efficiency coin cell.

[0078] In some embodiments, the layered oxide cathode material of the present invention is a near-pure phase. To evaluate the crystallinity of the layered oxide cathode material of the present invention, two parameters, α and β, are introduced to characterize the proportional relationship between the peak area and peak intensity of the CuO impurity phase in the XRD pattern and the peak area and peak intensity of a specific peak in the layered oxide cathode material, respectively. The closer α and β are to 0, the less CuO impurity phase is in the product. The calculation methods for α and β are as follows:

[0079] α=(AI (-111) %+AI (111) %) / (AI (003) %+AI (104) %)

[0080] β=(HI (-111) %+HI (111) %) / (HI (003) %+HI (104) %)

[0081] In the above formula, AI (003) % represents the ratio of the peak area of ​​peak (003) in the XRD pattern of the layered oxide cathode material to the peak area of ​​the highest peak in the XRD pattern; AI (104) % represents the ratio of the peak area of ​​peak (104) in the XRD pattern of the layered oxide cathode material to the peak area of ​​the highest peak in the XRD pattern; HI (003) % represents the ratio of the peak value (i.e., peak intensity, the same below) of the (003) peak in the XRD spectrum of the layered oxide cathode material to the peak value of the highest peak in the XRD spectrum; HI (104) % represents the ratio of the peak value of peak (104) in the XRD pattern of the layered oxide cathode material to the peak value of the highest peak in the XRD pattern; AI (-111) % represents the ratio of the peak area of ​​the (-111) peak of the CuO impurity phase in the XRD pattern of the layered oxide cathode material to the peak area of ​​the highest peak in the XRD pattern; AI (111) % represents the ratio of the peak area of ​​the (111) peak of the CuO impurity phase in the XRD pattern of the layered oxide cathode material to the peak area of ​​the highest peak in the XRD pattern; HI (-111) % represents the ratio of the peak value of the (-111) peak of the CuO impurity phase in the XRD pattern of the layered oxide cathode material to the peak value of the highest peak in the XRD pattern; HI (111) % represents the ratio of the peak value of the (111) peak of the CuO impurity phase in the XRD pattern of the layered oxide cathode material to the peak value of the highest peak in the XRD pattern. When measuring the XRD pattern (see the Examples section for specific measurement methods), the same sample can be tested multiple times, and then the average value of each test result can be substituted into the above formula to calculate α and β.

[0082] Furthermore, α / β indirectly represents the average full width at half maximum (FWHM) of the CuO impurity peaks. A smaller α / β mainly indicates that α approaches 0 more rapidly, suggesting that the CuO impurity content is low and the relatively large grains are sporadic precipitations, rather than widespread precipitation consisting of many discrete small grains.

[0083] In some embodiments, in the layered oxide cathode material of the present invention, α < 0.0500, β < 0.0200, and α / β < 2.5000.

[0084] The evaluation criteria of this invention start from the basic indicators of the material and use two indicators, peak area ratio and peak intensity ratio, to evaluate the crystallinity in a coordinated manner. This helps to reduce detection errors, improve the accuracy of the evaluation results, and has high reliability, making it possible to detect impurity phases in layered oxide cathode materials.

[0085] In the general formula of the layered oxide cathode material of the present invention, 0.60 ≤ x ≤ 1.20, preferably 0.70 ≤ x ≤ 1.20, more preferably 0.95 ≤ x ≤ 1.20, and even more preferably 0.95 ≤ x ≤ 1.02. As examples, x is 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91. 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, or any two of the above values ​​within the range.

[0086] In the general formula of the layered oxide cathode material of the present invention, 0.05 ≤ a ≤ 0.40, preferably 0.05 ≤ a ≤ 0.30. As an example, a is 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, or within any two of the above values.

[0087] In the general formula of the layered oxide cathode material of the present invention, 0 < y ≤ 0.30, preferably 0.04 ≤ y ≤ 0.20. As an example, y is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, or within any two of the above values.

[0088] Similarly, those skilled in the art will understand that parameters b, c, and d may also be included in any specific value within the defined range or in a new range consisting of any specific values ​​within the range. For example, in some embodiments, 0.03 ≤ b ≤ 0.70, preferably 0.03 ≤ b ≤ 0.60. For example, parameter b is 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0. 43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, or any two of the above values ​​within a range, and / or 0.10 ≤ c ≤ 0.45, preferably 0.10 ≤ c ≤ 0.40, for example, parameter c is 0.10, 0.11, 0.12, 0. 13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, or any two of the above values, and / or 0.10 ≤ d ≤ 0.45, preferably 0.10 ≤ d ≤ 0. 40, for example, parameter d is 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, or within any two of the above values.

[0089] In the general formula of the layered oxide cathode material of the present invention, nδ = -0.05 to 0.15, for example, it can be -0.05, -0.04, -0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, or within any two of the above values, for example, nδ = -0.02 to 0.02, or nδ = 0. In some embodiments, 0 < n ≤ 0.1, -1 ≤ δ ≤ 3, for example, n is 0.02, 0.05, 0.08, 0.10, and δ is -1, 0, 1, 2, or 3. Those skilled in the art will understand that the parameters x, a, b, c, d, y, n, and δ in the general formula of layered oxide cathode materials enable the general formula to satisfy chemical equilibrium.

[0090] Further research by the inventors revealed that when the molar ratio of each element is within the range specified below, it is beneficial to further improve the electrochemical performance of the corresponding sodium-ion secondary battery, such as the first-cycle efficiency.

[0091] In some embodiments, the Al / Mg molar ratio is from 1:3.50 to 1:0.25, and the Ti / Mg molar ratio is from 1:6.00 to 1:0.05. Preferably, the Al / Mg molar ratio is from 1:3.00 to 1:0.25. More preferably, the Ti / Mg molar ratio is from 1:5.00 to 1:0.05, more preferably from 1:3.00 to 1:0.05. As examples, the Al / Mg molar ratio is 1:0.25, 1:0.50, 1:0.75, 1:1.00, 1:1.25, 1:1.50, 1:1.75, 1:2.00, 1:2.25, 1:2.50, 1:2.75, 1:3.00, 1:3.25, 1:3.50, or within any two of the above values. As an example, the molar ratio of Ti / Mg is 1:0.05, 1:0.06, 1:0.15, 1:0.20, 1:0.33, 1:0.40, 1:0.50, 1:0.60, 1:0.70, 1:0.80, 1:0.90, 1:1.00, 1:1.20, 1:1.40, 1:1.60, 1:1.80, 1:2.00, 1:2.25, 1:2.50, 1:2.75, 1:3.00, 1:3.50, 1:4.00, 1:4.50, 1:5.00, 1:5.50, 1:6.00, or within any two of the above values.

[0092] In a preferred embodiment, the ratio y / a of the subscript y of the dopant element M to the subscript a of the element Cu is 1:9.00 to 1:0.10, preferably 1:7.50 to 1:0.25, and more preferably 1:3.00 to 1:0.25. As an example, y / a can be 1:0.10, 1:0.15, 1:0.25, 1:0.35, 1:0.50, 1:0.60, 1:0.75, 1:1.00, 1:1.25, 1:1.50, 1:1.75, 1:2.00, 1:2.25, 1:2.50, 1:2.86, 1:3.00, 1:3.75, 1:4.25, 1:5.00, 1:6.00, 1:7.50, 1:8.00, 1:8.50, 1:9.00, or any two of the above values. When the molar ratio of the total dopant content to the Cu content is within the above range, it is beneficial to further eliminate CuO impurity peaks and improve the electrochemical performance of the corresponding sodium-ion secondary battery, such as the first-efficiency coin cell.

[0093] In some embodiments, the molar ratio of Mg / Cu is 1:40 to 1:1.00, preferably 1:30 to 1:2.00; and / or the molar ratio of Al / Cu is 1:30 to 1:1.50, preferably 1:20 to 1:3.50; and / or the molar ratio of Ti / Cu is 1:40 to 1:0.25, preferably 1:30 to 1:0.25, more preferably 1:20 to 1:0.25. As an example, the molar ratio of Mg / Cu is 1:1.00, 1:1.50, 1:2.00, 1:3.50, 1:5.00, 1:6.00, 1:7.50, 1:10.00, 1:15.00, 1:20.00, 1:30.00, 1:35.00, 1:40.00, or any two of the above values, and / or the molar ratio of Al / Cu is 1:1.50, 1:2.00, 1:2.50, 1:3.50, 1:5.00, 1:7.50, 1:10.00, 1:12.50, 1:1:1.50, 1:2.00, 1:2.50, 1:3.50, 1:5.00, 1:7.50, 1:10.00, 1:12.50, 1:1:1.00, ...1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1:1.50, 1: :15.00, 1:17.50, 1:20.00, 1:25.00, 1:30.00 or any two of the above values, and / or the molar ratio of Ti / Cu is 1:0.25, 1:0.28, 1:0.47, 1:1.00, 1:3.00, 1:5.00, 1:7.50, 1:10.00, 1:12.00, 1:15.00, 1:20.00, 1:25.00, 1:30.00, 1:35.00, 1:40.00 or any two of the above values.

[0094] In some embodiments, when the molar amount of the layered oxide cathode material is 1 mole, the content of the dopant element Mg is 0.01 to 0.05 moles, preferably 0.01 to 0.03 moles. As an example, when the molar amount of the layered oxide cathode material is 1 mole, the content of the dopant element Mg is 0.01 moles, 0.02 moles, 0.03 moles, 0.04 moles, 0.05 moles, or within any two of the above contents.

[0095] In some embodiments, the ratio d / a of the subscript d of element Mn to the subscript a of element Cu is 1:0.15 to 1:0.95, preferably 1:0.15 to 1:0.60. As examples, d / a is 1:0.15, 1:0.20, 1:0.35, 1:0.40, 1:0.45, 1:0.50, 1:0.55, 1:0.60, 1:0.70, 1:0.80, 1:0.95, or any combination of the above values.

[0096] In some embodiments, the ratio a / x of the subscript 'a' of element Cu to the subscript 'x' of element Na is 1:3.5 to 1:24, preferably 1:4.5 to 1:24. As examples, a / x is 1:3.50, 1:4.50, 1:4.75, 1:6.80, 1:8.00, 1:10.00, 1:12.00, 1:15.00, 1:18.00, 1:20.00, 1:24.00, or any combination of the above values.

[0097] In some embodiments, the dopant element M is selected from any one of Mg+Al+Ti, or Mg+Al+Ti+Li, or Mg+Al+Ti+K, or Mg+Al+Ti+Sn.

[0098] In some embodiments, the layered oxide cathode material has an O3-type crystal structure.

[0099] In some embodiments, the pH of the layered oxide cathode material is from 11.00 to 13.00.

[0100] The particle size D50 of the layered oxide cathode material of the present invention is not particularly limited, and can be, for example, 1-500 μm, specifically within any two of the following ranges: 1, 5, 10, 15, 20, 25, 50, 100, 200, 300, 400, 500 μm. The particle size can be measured using laser scattering methods commonly used in the art. It can be measured using instruments commonly used in the art, such as the MASTERSIZER-3000 Malvern particle size analyzer.

[0101] Preparation method of layered oxide cathode materials

[0102] Those skilled in the art will understand that the layered oxide cathode material of the present invention can be prepared by various methods. As an example, a second aspect of the present invention provides a method for preparing a layered oxide cathode material according to the first aspect of the present invention, comprising the following steps:

[0103] Step a: Mix Na source, Cu source, Ni source, Fe source, Mn source and M source uniformly in stoichiometric ratio to obtain a mixed precursor;

[0104] Step b: Sinter the precursor obtained in step a; and

[0105] Step c: Cool the product obtained in step b, and optionally crush and sieve it.

[0106] Step a

[0107] In step a, the Na source, Cu source, Ni source, Fe source, Mn source, and optional M source are uniformly mixed in stoichiometric ratio to obtain a mixed precursor.

[0108] The sodium source can be any sodium-containing compound known to those skilled in the art for preparing positive electrode materials for sodium-ion secondary batteries. The sodium source can be one or more forms of sodium-containing oxides, hydroxides, salts, etc. In one or more embodiments, the Na source can be one or more compounds selected from: sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, sodium oxalate, sodium hydroxide, and sodium oxide.

[0109] The Cu source can be any copper-containing compound known to those skilled in the art for preparing cathode materials for sodium-ion secondary batteries. In one or more embodiments, the Cu source can be one or more compounds selected from the following: copper carbonate, copper nitrate, copper acetate, copper oxalate, copper hydroxide, and copper oxide.

[0110] The Ni source can be any nickel-containing compound known to those skilled in the art for preparing cathode materials for sodium-ion secondary batteries. In one or more embodiments, the Ni source can be one or more compounds selected from the following: nickel carbonate, nickel nitrate, nickel acetate, nickel oxalate, nickel hydroxide, and nickel oxide.

[0111] The Fe source can be any nickel-containing compound known to those skilled in the art for preparing cathode materials for sodium-ion secondary batteries. In one or more embodiments, the Fe source can be one or more compounds selected from the following: iron carbonate, iron nitrate, iron acetate, iron oxalate, iron hydroxide, and iron oxide.

[0112] The element M in the M source includes Mg, Al, and Ti, as well as one or more of the following elements: Ca, B, Li, K, W, Mo, Sr, Y, Sn, Sb, and Ce. In some embodiments, the M source is one or more compounds selected from the following forms: carbonates, nitrates, acetates, oxalates, hydroxides, and oxides.

[0113] The mixing can be carried out by any suitable mixing method known to those skilled in the art. In some embodiments, the mixing in step a is carried out by dry mixing or wet mixing, preferably by sol-gel mixing or co-precipitation mixing.

[0114] Step b

[0115] In step b, the precursor obtained in step a is sintered.

[0116] The sintering temperature is not particularly limited, and can be 700 to 1200°C, preferably 800 to 1100°C, and more preferably 900 to 1000°C. In one or more embodiments, the sintering temperature may be, for example, 700, 710, 720, 730, 740, 750, 760, 770, 780, 790, 800, 810, 820, 830, 840, 850, 860, 870, 880, 890, 900, 910, 920, 930, 940, 950, 960, 970, 980, 990, 1000, 1010, 1020, 1030, 1040, 1050, 1060, 1070, 1080, 1090, 1100, 1110, 1120, 1130, 1140, 1150, 1160, 1170, 1180, 1190, 1200°C, or a range defined by any two of the above values.

[0117] The sintering time is not particularly limited and can be 5 to 36 hours, preferably 8 to 36 hours, and more preferably 12 to 20 hours. In some embodiments, the sintering time is 5, 10, 12, 14, 16, 18, 20, 25, 30, 36 hours, or any two of the above values.

[0118] In some embodiments, the sintering in step b is carried out in an oxidizing atmosphere, preferably compressed air or oxygen. As an example, the oxygen content in the oxidizing atmosphere is >98.5% (volume fraction), and the absolute pressure of the compressed air is >0.6 MPa, for example, 0.8 MPa.

[0119] The heating rate during sintering is not particularly limited and can be 1 to 10 °C / min, preferably 2 to 5 °C / min, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 °C / min, or any two of the above values.

[0120] Step c

[0121] In step c, the product obtained in step b is cooled and optionally crushed and sieved.

[0122] The cooling, crushing, and sieving can be performed by any suitable means known to those skilled in the art.

[0123] Positive electrode composition

[0124] A third aspect of the present invention provides a positive electrode composition for use in sodium-ion secondary batteries, comprising a layered oxide positive electrode material according to a first aspect of the present invention.

[0125] In addition to the layered oxide cathode material of the present invention, the cathode composition for sodium-ion secondary batteries may also include conductive agents, binders, and any other substances that may be used by those skilled in the art as needed, such as dispersants and additives for improving stability.

[0126] In some embodiments, based on the dry weight of the cathode composition for sodium-ion secondary batteries, the content of the layered oxide cathode material can be a commonly used amount in the art, for example, 70-95% by weight, or, for example, 80-90% by weight.

[0127] There are no particular limitations on the type of conductive agent, as long as it enhances the conductivity of the positive electrode and does not adversely affect the performance of the positive electrode material. Those skilled in the art can select conductive agents commonly used in the art according to actual needs. As an example, the conductive agent used in the aforementioned positive electrode composition for sodium-ion secondary batteries may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0128] In some embodiments, based on the dry weight of the positive electrode composition for sodium-ion secondary batteries, the content of the conductive agent may be a commonly used amount in the art, for example, 1-10% by weight, or for example, 2-5% by weight.

[0129] There are no particular limitations on the binder, as long as it enhances the adhesion between the positive electrode active material particles and the adhesion to the current collector, and does not adversely affect the performance of the positive electrode material. Those skilled in the art can select according to actual needs. As an example, the binder used in the said positive electrode composition for sodium-ion secondary batteries may be selected from polyfluoroolefin binders such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA) or their modified (e.g., modified with carboxylic acid, acrylic acid, acrylonitrile, etc.) derivatives, as well as one or more of styrene-butadiene rubber, acrylic resin, carboxymethyl cellulose, polyvinyl alcohol (PVA), etc.

[0130] In some embodiments, the binder content is 1-10% by weight, for example 2-5% by weight, based on the dry weight of the positive electrode composition for the sodium-ion secondary battery.

[0131] The positive electrode composition may be in slurry form, meaning it may further include a solvent. The positive electrode composition may also be in dry form, meaning it does not include a solvent, for example, it may be in the form of a layer of positive electrode active material disposed on a positive electrode current collector.

[0132] Sodium-ion secondary batteries

[0133] A fourth aspect of the present invention provides a sodium-ion secondary battery. A sodium-ion secondary battery typically includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0134] In some embodiments, the sodium-ion secondary battery may also include an outer packaging for encapsulating the electrode assembly and electrolyte. For example, the outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc., or it may be a soft pack, such as a pouch, for example a soft pack made of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0135] There are no particular restrictions on the shape of sodium-ion secondary batteries; they can be cylindrical, square, or any other shape.

[0136] Sodium-ion secondary batteries can be prepared by methods commonly used in the art, for example, by forming a cell from positive electrode, negative electrode and separator through a winding process or a stacking process, and then injecting an electrolyte.

[0137] positive electrode

[0138] The positive electrode (or positive electrode sheet) includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising, for example, a dry form of the positive active material composition of the third aspect of the present invention. The positive electrode also forms an aspect of the present invention.

[0139] There are no particular limitations on the positive electrode current collector, and any positive electrode current collector commonly used by those skilled in the art can be used. As an example, the positive electrode current collector can be a metal foil such as aluminum foil, nickel foil, or a composite current collector. Composite current collectors can be formed by forming a metallic material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), 1,3-propanesulfonate lactone (PS), polyethylene (PE), etc.), but the present invention is not limited to these materials.

[0140] The positive electrode sheet can be prepared according to methods commonly used in this field.

[0141] For example, the positive electrode can be formed by uniformly dispersing the positive electrode active material, conductive agent, and binder in a solvent (e.g., N-methylpyrrolidone (NMP)) to obtain a positive electrode slurry; coating the slurry onto a positive electrode current collector, drying, and pressing.

[0142] Alternatively, the positive electrode can also be formed by uniformly dispersing the positive electrode active material, conductive agent, and binder in a solvent (e.g., N-methylpyrrolidone (NMP)) to obtain a positive electrode slurry; casting the positive electrode slurry on a separate carrier, drying it, separating the resulting positive electrode film from the carrier, and laminating it onto the positive electrode current collector.

[0143] negative electrode

[0144] The negative electrode (or negative electrode sheet) may be a sodium metal sheet, or it may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0145] There are no particular limitations on the negative electrode current collector, and any negative electrode current collector commonly used by those skilled in the art can be used. As an example, the negative electrode current collector can be a metal foil such as copper foil, or a composite current collector. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.), but the present invention is not limited to these materials.

[0146] In some embodiments, the negative electrode active material may be an active material commonly used by those skilled in the art. For example, the negative electrode active material may be one or more of natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon-based materials, tin-based materials, lithium titanate, and metallic sodium. The silicon-based material may be one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys, and the tin-based material may be one or more of elemental tin, tin oxide compounds, and tin alloys.

[0147] In addition to the negative electrode active material, the negative electrode active material layer may also include binders, conductive agents, and any other optional additives such as thickeners.

[0148] There are no special requirements for the negative electrode conductive agent. As an example, the conductive agent may be selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0149] In some embodiments, the content of the conductive agent may be 1 to 10% by weight, for example 2-5% by weight, based on the total weight (dry weight) of the negative electrode active material layer.

[0150] There are no special requirements for the negative electrode binder. As an example, the binder is selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), styrene-butadiene rubber (SBR), waterborne acrylic resin, and carboxymethyl cellulose (CMC).

[0151] In some embodiments, the binder content may be 1 to 10% by weight, for example 2-5% by weight, based on the total weight (dry weight) of the negative electrode active material layer.

[0152] The negative electrode can be prepared according to methods commonly used in the art.

[0153] For example, the negative electrode can be formed by uniformly dispersing the negative electrode active material and optionally a conductive agent, binder and thickener in a solvent (e.g. N-methylpyrrolidone (NMP) or deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, drying and pressing.

[0154] Alternatively, the negative electrode can also be formed by uniformly dispersing the negative electrode active material and optionally a conductive agent, binder and thickener in a solvent (e.g. N-methylpyrrolidone (NMP) or deionized water) to form a negative electrode slurry; casting the negative electrode slurry on a separate carrier, drying it, separating the resulting negative electrode film from the carrier and laminating it onto a negative electrode current collector.

[0155] electrolytes

[0156] The electrolyte acts as a conductor of ions between the positive and negative electrodes. There are no particular limitations on the electrolyte, and it can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes, gel electrolytes, and liquid electrolytes (i.e., electrolyte solutions).

[0157] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution comprises an organic aprotic solvent and an electrolyte sodium salt.

[0158] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0159] In some embodiments, the electrolyte sodium salt may be selected from one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroborate (NaBF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium di(oxalate borate) (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodi(oxalate phosphate) (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0160] In some embodiments, the concentration of sodium ions in the electrolyte is 0.2 to 2 mol / L, for example 0.5-1.0 mol / L.

[0161] In some embodiments, the electrolyte may optionally include additives. As an example, the additives may include those that aid in the formation of a negative electrode film or a positive electrode film, and may also include additives that improve battery performance, such as those that improve the battery's high-temperature or low-temperature performance.

[0162] diaphragm

[0163] There are no particular limitations on the membrane, and commonly used porous membranes with electrochemical and chemical stability can be used, such as single-layer or multi-layer films made of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. When using a solid electrolyte, the membrane can also be omitted.

[0164] use

[0165] The fifth aspect of the invention provides the use of the sodium-ion secondary battery according to the fourth aspect of the invention in energy storage devices for solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies or communication base stations.

[0166] Those skilled in the art will understand that the sodium-ion secondary battery of the fourth aspect of the present invention can also be used for other purposes. For example, the sodium-ion secondary battery can be used as a power supply or energy storage unit in mobile devices (e.g., mobile phones), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, electric bicycles, electric scooters, etc.), electric trains, etc.

[0167] Example

[0168] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0169] I. Preparation Examples

[0170] Comparative Example 1

[0171] Preparation of O3-type Na 1.02 Cu 0.05 Fe 0.34 Ni 0.28 Mn 0.33 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, and MnO2, the raw materials for the process, were weighed according to their elemental stoichiometric ratios. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 1050℃ in an oxygen atmosphere (oxygen volume fraction > 98.5%) for 20 h, with a heating rate of 2℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 9.892 μm, denoted as C1.

[0172] The particle size D50 of each comparative example and embodiment was tested as follows: using a Malvern particle size analyzer (MASTERSIZER-3000), 1g of the material to be tested was taken, and pure water was used as the dispersion liquid. The particle size and volume distribution were tested under ultrasonic conditions, and the average value was taken for three parallel tests.

[0173] Comparative Example 2

[0174] Preparation of O3-type Na 1.02 Cu 0.20 Fe 0.34 Ni 0.13 Mn 0.33 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, and MnO2, the raw materials for the process, were weighed according to their elemental stoichiometric ratios. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 950℃ in a compressed air atmosphere (absolute pressure 0.8MPa, the same below) for 15h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 10.013μm, denoted as C2.

[0175] Comparative Example 3

[0176] Preparation of O3-type Na 0.95 Li 0.04 Cu 0.06 Fe 0.37 Ni 0.18 Mn 0.37 Al 0.02 Ti 0.02 Ca 0.02 O2: Na2CO3, Li2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Al2O3, TiO2, and CaO were weighed according to their elemental stoichiometric ratios. After uniform mixing, the mixture was dried to obtain a precursor. The resulting precursor was sintered at 960℃ in an oxygen atmosphere (oxygen volume fraction > 98.5%) for 24 h, with a heating rate of 3℃ / min. After cooling to room temperature, the product was pulverized and sieved to obtain a product with a particle size D50 = 10.124 μm, denoted as C3.

[0177] Comparative Example 4

[0178] Preparation of O3-type Na 1.10 Cu 0.30 Fe 0.33 Ni 0.03 Mn 0.30 Mg 0.01 Al 0.02 Ti 0.01 V 0.01O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, TiO2, and V2O5, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 920℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 16h, with a heating rate of 2℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 10.215μm, denoted as C4.

[0179] Comparative Example 5

[0180] Preparation of O3-type Na 1.01 Cu 0.15 Fe 0.34 Ni 0.08 Mn 0.33 Al 0.01 Ti 0.02 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Al2O3, and TiO2, the raw materials for the process, were weighed according to their elemental stoichiometric ratios. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 950℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 18h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 9.893μm, denoted as C5.

[0181] Example 1

[0182] Preparation of O3-type Na 1.01 Cu 0.15 Fe 0.34 Ni 0.08 Mn 0.33 Mg 0.02 Al 0.01 Ti 0.02 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 970℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 14h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 9.976μm, denoted as E1.

[0183] Example 2

[0184] Preparation of O3-type Na 0.95 Li 0.04 Cu 0.2 Fe 0.37 Ni0.04 Mn 0.37 Mg 0.01 Al 0.01 Ti 0.01 O2: Na2CO3, Li2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to their elemental stoichiometric ratios. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 960℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 15h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 10.532μm, denoted as E2.

[0185] Example 3

[0186] Preparation of O3-type Na 1.10 Cu 0.30 Fe 0.34 Ni 0.03 Mn 0.33 Mg 0.01 Al 0.02 Ti 0.01 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 980℃ in an oxygen atmosphere (oxygen volume fraction > 98.5%) for 18 h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 10.723 μm, designated as E3.

[0187] Example 4

[0188] Preparation of O3-type Na 0.70 Cu 0.07 Fe 0.18 Ni 0.15 Mn 0.40 Mg 0.03 Al 0.02 Ti 0.15 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 900℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 14h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 9.782μm, denoted as E4.

[0189] Example 5

[0190] Preparation of O3-type Na 1.20 Cu 0.05 Fe 0.10 Ni 0.60 Mn 0.10 Mg 0.01 Al 0.01 Ti 0.18 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 1050℃ in an oxygen atmosphere (oxygen volume fraction > 98.5%) for 20h, with a heating rate of 2℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 10.783μm, denoted as E5.

[0191] Example 6

[0192] Preparation of O3-type Na 0.90 Cu 0.20 Fe 0.35 Ni 0.04 Mn 0.37 Mg 0.01 Al 0.01 Ti 0.01 Sn 0.01 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, TiO2, and SnO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 950℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 15h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 9.682μm, denoted as E6.

[0193] Example 7

[0194] Preparation of O3-type Na 1.02 Cu 0.15 Fe 0.34 Ni 0.08 Mn 0.33 Mg 0.03 Al 0.01 Ti 0.01O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 920℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 13h, with a heating rate of 2℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 10.332μm, denoted as E7.

[0195] Example 8

[0196] Preparation of O3-type Na 1.02 Cu 0.15 Fe 0.34 Ni 0.08 Mn 0.33 Mg 0.01 Al 0.01 Ti 0.03 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 930℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 14h, with a heating rate of 3℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 9.972μm, denoted as E8.

[0197] Example 9

[0198] Preparation of O3-type Na 1.10 Cu 0.30 Fe 0.34 Ni 0.03 Mn 0.33 Mg 0.03 Al 0.02 Ti 0.01 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 910℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 15h, with a heating rate of 2℃ / min. After cooling to room temperature, it was pulverized and sieved to obtain a product with a particle size D50 = 10.811μm, denoted as E9.

[0199] Example 10

[0200] Preparation of O3-type Na 1.10 Cu 0.30 Fe 0.34Ni 0.03 Mn 0.33 Mg 0.05 Al 0.02 Ti 0.01 O2: Na2CO3, CuO, Fe2O3, Ni(OH)2, MnO2, Mg(OH)2, Al2O3, and TiO2, the raw materials for the process, were weighed according to the stoichiometric ratio. After being mixed evenly, they were dried to obtain a mixed precursor. The obtained mixed precursor was sintered at 900℃ in a compressed air atmosphere (absolute pressure 0.8MPa) for 12h, with a heating rate of 3℃ / min. After cooling to room temperature, it was crushed and sieved to obtain a product with a particle size D50 = 9.792μm, denoted as E10.

[0201] II. Manufacturing of Button Cells

[0202] The products of Examples 1 to 10 and Comparative Examples 1 to 5 were placed at a constant humidity of 50% for 30 min, respectively. Then, they were used as active materials and mixed with SP (Swiss Temi High Conductivity Carbon Black SUPERP) at a mass ratio of 90:5:5 (SOLVAY PVDF 5130). N-methylpyrrolidone (NMP) was then added to prepare a viscous adhesive. This adhesive was coated onto aluminum foil (16 μm thick) and then baked in a vacuum drying oven at 120°C for 12 h to obtain a positive electrode sheet (active material layer thickness 34 ± 5 ​​μm). A sodium metal sheet (Aladdin) was used as the counter electrode (thickness 300 ± 50 μm). A 2032 coin cell was assembled in an Ar atmosphere-protected glove box using a glass fiber (Waterman) membrane (675 μm thick) and a NaPF6 solution with a sodium ion concentration of 1 mol / L (a mixture of EC and DMC in a volume ratio of EC / DMC = 1:1) (Alfa) as the electrolyte.

[0203] III. Evaluation of the Implementation Examples

[0204] Evaluation Example 1: X-ray Diffraction Analysis (XRD)

[0205] XRD analysis was performed on the materials prepared in Comparative Examples 1-5 and Examples 1-10. X-ray diffractometer (model Bruker D8 ADVANCE) was used with a copper target (Cu-Kα) (accelerating voltage 40 kV, current 40 mA) for measurements (λ = 1.54056 nm), ranging from 10 to 80 degrees, with a step size of 0.02 degrees, a time of 0.2 seconds, and a total duration of 712 seconds. The results are shown in... Figure 1 middle.

[0206] When calculating α and β, five tests were performed on each sample, and then the AI ​​was applied. (003) % HI(003) The average value of parameters such as percentage was taken, and the calculation was performed according to the formula described above. The calculation results are shown in Table 1.

[0207] Evaluation Example 2: pH Test

[0208] pH tests were performed on the materials prepared in Comparative Examples 1-5 and Examples 1-10. An appropriate amount of cathode material was added to a corresponding amount of distilled water at a mass ratio of layered oxide cathode material to distilled water of 1:20. The mixture was magnetically stirred at 600±20 r / min for 10 min to ensure uniform mixing. After the mixture was allowed to stand for 5 min, the pH was measured using a pH meter (METTLER TOLEDO pH meter FE22-Standard) at a constant temperature of 25°C. This pH value represents the pH of the corresponding material. The test results are shown in Table 1.

[0209] Evaluation Example 3: Measurement of First Effect of Button Charge

[0210] After the 2032 coin cell is assembled, the cell is tested at room temperature within a voltage range of 2.5 to 4.0V and cycled at 0.1C for 3 weeks. The first week discharge specific capacity / first week charge specific capacity × 100% is the first efficiency of the coin cell.

[0211] The experimental results of comparative examples C1-C5 and examples E1-E10 are summarized in Table 1.

[0212] Table 1. Experimental results of Comparative Examples C1-C5 and Examples E1-E10

[0213]

[0214] Combining Table 1 and Figure 1 It can be seen that, without doping, the products of comparative examples C1 and C2 have lower crystallinity and more CuO impurity phase. Furthermore, combining the results of C1 and C2, it can be seen that, without Mg, Al, and Ti doping, as the Cu content increases from 0.05 to 0.20, the CuO impurity phase in the XRD pattern significantly increases, and the corresponding α and β values ​​also increase substantially, ultimately leading to a significant decrease in the first-time efficiency (1st coin cell efficiency) of the corresponding sodium-ion secondary battery (from 88.11% to 72.01%). Therefore, it is evident that, without Mg, Al, and Ti doping, increasing the Cu content will lead to an increase in the CuO impurity phase in the product, thereby deteriorating battery performance.

[0215] See comparative examples C3-C5 and Figure 1 It can be seen that doping with Al, Ti, and Ca (or V) reduces the CuO impurity phase in the XRD pattern, thereby improving the first-time efficiency of the sodium-ion secondary battery. However, the resulting product still contains a relatively large amount of CuO impurity phase, resulting in a still low first-time efficiency for the sodium-ion secondary battery.

[0216] See Examples E1-E10 and Figure 1 It can be seen that when Mg, Al, and Ti are doped simultaneously, the CuO impurity phase in the XRD pattern of the product is further reduced, and the first-time efficiency of the corresponding sodium-ion secondary battery is further improved. Furthermore, as shown in Examples E1-E10, changing the ratio of elements in the layered oxide cathode material, especially the molar ratios of Ti / Mg and Al / Mg, and the ratio y / a of the content y of dopant element M to the content a of Cu, can further eliminate the CuO impurity phase and further improve the first-time efficiency of the corresponding sodium-ion secondary battery. In particular, when the molar ratio of Ti / Mg is 1:0.06 to 1:3.00, and / or y / a is 1:0.25 to 1:3.00, the CuO impurity phase is less (or even completely eliminated, see Examples E1 and E2), and the first-time efficiency of the corresponding sodium-ion secondary battery is also higher.

[0217] The above description is merely an exemplary embodiment of the present invention. It should be noted that those skilled in the art can make improvements to the present invention without departing from the inventive concept, and all such improvements fall within the scope of protection of the present invention.

Claims

1. A layered oxide cathode material having the following general formula: So x Cu a Ni b Feb c Mr d M y O 2+nδ , Where 0.61≤x≤1.20, 0.05≤a≤0.40, 0.03≤b≤0.70, 0.10≤c≤0.45, 0.10≤d≤0.45, 0<y≤0.30, and satisfying x+2a+2b+3c+3d+2y<4<x+2a+3b+3c+4d+4y, 0.95≤a+b+c+d+y≤1.05, 0<n≤0.1, -1≤δ≤3; and M includes Mg+Al+Ti+Li.

2. The layered oxide cathode material according to claim 1, wherein the molar ratio of Al / Mg is from 1:3.50 to 1:0.25, and the molar ratio of Ti / Mg is from 1:6.00 to 1:0.

05.

3. The layered oxide cathode material according to claim 1 or 2, wherein the range of y / a is from 1:9.00 to 1:0.

10.

4. The layered oxide cathode material according to claim 1 or 2, wherein the molar ratio of Mg / Cu is from 1:40 to 1:1.00; and / or The molar ratio of Al / Cu is from 1:20 to 1:3.50; and / or The molar ratio of Ti / Cu is from 1:40 to 1:0.

25.

5. The layered oxide cathode material according to claim 1 or 2, wherein M is Mg + Al + Ti + Li.

6. The layered oxide cathode material according to claim 1 or 2, wherein the layered oxide cathode material has an O3-type crystal structure.

7. The layered oxide cathode material according to claim 1, wherein 0.69 ≤ x ≤ 1.

20.

8. The layered oxide cathode material according to claim 1, wherein 0.05 ≤ a ≤ 0.

30.

9. The layered oxide cathode material according to claim 1, wherein 0.03 ≤ b ≤ 0.

60.

10. The layered oxide cathode material according to claim 1, wherein 0.04 ≤ y ≤ 0.

20.

11. The layered oxide cathode material according to claim 1, wherein nδ = -0.02 to 0.

02.

12. The layered oxide cathode material according to claim 1, wherein nδ = 0.

13. The layered oxide cathode material according to claim 1, wherein M further comprises one or more of Ca, B, K, W, Mo, Sr, Y, Sn, Sb, and Ce.

14. The layered oxide cathode material according to claim 2, wherein the molar ratio of Al / Mg is from 1:3.00 to 1:0.

25.

15. The layered oxide cathode material according to claim 2, wherein the molar ratio of Ti / Mg is from 1:5.00 to 1:0.

05.

16. The layered oxide cathode material according to claim 3, wherein the y / a ratio ranges from 1:7.50 to 1:0.

25.

17. The layered oxide cathode material according to claim 4, wherein the molar ratio of Mg / Cu is from 1:30 to 1:2.

00.

18. The layered oxide cathode material according to claim 4, wherein the molar ratio of Al / Cu is from 1:20 to 1:3.

50.

19. The layered oxide cathode material according to claim 4, wherein the molar ratio of Ti / Cu is from 1:30 to 1:0.

25.

20. A method for preparing the layered oxide cathode material according to any one of claims 1 to 19, comprising the following steps: Step a: Mix Na source, Cu source, Ni source, Fe source, Mn source and M source uniformly in stoichiometric ratio to obtain a mixed precursor; Step b: Sinter the precursor obtained in step a; and Step c: Cool the product obtained in step b.

21. The method according to claim 20, wherein step c further comprises pulverizing and sieving after cooling.

22. The method of claim 20, wherein The Na source is one or more compounds selected from the following: sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, sodium oxalate, sodium hydroxide, and sodium oxide; The Cu source is one or more compounds selected from the following: copper carbonate, copper nitrate, copper acetate, copper oxalate, copper hydroxide, and copper oxide; The Ni source is one or more compounds selected from the following: nickel carbonate, nickel nitrate, nickel acetate, nickel oxalate, nickel hydroxide, and nickel oxide; The Fe source is one or more compounds selected from the following: iron carbonate, iron nitrate, iron acetate, iron oxalate, iron hydroxide, and iron oxide; The Mn source is one or more compounds selected from the following: manganese carbonate, manganese nitrate, manganese acetate, manganese oxalate, manganese hydroxide, and manganese oxide; and The M source is one or more compounds selected from the following forms: carbonates, nitrates, acetates, oxalates, hydroxides, and oxides.

23. The method of claim 20, wherein the mixing in step a is performed by dry mixing or wet mixing.

24. The method of claim 23, wherein the wet mixing is performed by a sol-gel method or a co-precipitation method.

25. The method according to claim 20 or 21, wherein the sintering in step b is carried out in an oxidizing atmosphere.

26. The method of claim 25, wherein the oxidizing atmosphere is compressed air or oxygen.

27. The method according to claim 20 or 21, wherein the sintering temperature in step b is 700 to 1200°C and the sintering time is 8 h to 36 h.

28. The method of claim 27, wherein the sintering temperature in step b is 800 to 1100°C.

29. The method according to claim 27, wherein the sintering time in step b is 12 h to 20 h.

30. A cathode composition for use in sodium-ion secondary batteries, comprising the layered oxide cathode material according to any one of claims 1 to 19.

31. A sodium-ion secondary battery comprising the positive electrode composition according to claim 30.

32. The use of the sodium-ion secondary battery as described in claim 31 in energy storage devices for solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies or communication base stations.

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