A layered sodium-ion battery cathode material, a preparation method thereof and a sodium-ion battery

Abstract

The present application relates to a kind of layered sodium ion battery positive electrode material and its preparation method and sodium ion battery, belong to sodium ion battery technical field, to solve the problem of high sodium content in prior art high residual alkali content of positive electrode material, in turn affect the capacity of sodium ion battery and other performance.The specific ratio of each element in the positive electrode material of the present application improves the sodium content, improves the proportion of active sodium of the material, and the sodium ion battery obtained has higher capacity, and the material of the present application can keep the residual alkali content within a reasonable range, the consistency and stability of the battery are good under the higher sodium content of the present application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a layered sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery. BACKGROUND

[0002] The energy density of sodium ion batteries is relatively low. Although the layered oxide positive electrode material has a high theoretical capacity, its available capacity is limited. It is not easy to introduce other elements on the basis of product standardization. The proportion adjustment involves subsequent new product development processes. The electrolyte is difficult to adapt at a higher voltage. Therefore, it is particularly important to find a means to improve the capacity within the existing voltage range on the basis of the existing process.

[0003] The existing capacity-improving means mainly include element doping at a higher voltage to improve the structure, proportion adjustment and the use of new materials. However, the current electrolyte system is difficult to adapt at a higher voltage. Element doping improvement requires the introduction of other elements, which is difficult to operate on the existing production line. After proportion adjustment, the performance of the material needs to be re-evaluated, and the subsequent system development needs to be completely overhauled, which is time-consuming and labor-intensive. The development of new materials is difficult, and the production process is also difficult to consider.

[0004] Too high a sodium content will result in a high alkalinity of the material. High residual alkali content will cause the cell slurry to gel easily, and gas will be produced during the charging and discharging process of the cell. Even high-nickel materials need to be washed, coated with multiple layers and doped with multiple elements to reduce the residual alkali content. However, the theoretical capacity of the material and the molar ratio of Na are directly linearly related. The amount of sodium affects the capacity of the material to some extent. The consistency and stability of the material can be improved at a higher sodium content. Therefore, on the basis of increasing the sodium content, specific materials are further sought to keep the residual alkali content within a reasonable range. SUMMARY

[0005] In view of the above analysis, the embodiments of the present application aim to provide a layered sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery, to solve the problem of high residual alkali content of the positive electrode material with high sodium content in the prior art, which affects the capacity and other properties of the sodium ion battery.

[0006] In one aspect, the present application provides a layered sodium ion battery positive electrode material, the general formula of the positive electrode material is Na x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 M a2 O 2+nδ ;

[0007] 0.9 < x2 < 0.98, 0.05 < y2 < 0.20, 0.32 < z2 < 0.40, 0.01 < s2 < 0.07, 0.08 < t2 < 0.22, 0.33 < u2 < 0.40, 0 < a2 < 0.05, 0.34 (y2 + z2 + t2 + u2) < u2 / x2 < 0.51 (y2 + z2 + t2 + u2), x2 + 2y2 + 3z2 + 3u2 + 2a2 + s2 + 2t2 < 4 < x2 + 2y2 + 4z2 + 3u2 + 4a2 + s2 + 3t2, y2 + z2 + a2 + s2 + t2 + u2 = 1, 0 < n < 0.05, -1 < δ < 3.

[0008] The M is one or more of Mg, Ca, B, Al, Li, K, Ag, Zr, Ti, W, Mo, Cr, Sr, Y, Cd, Sn, Sb, Ce.

[0009] Further, the positive electrode material has a general formula of Na x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 (M a21 M a22 )O 2+nδ , M a21 , M a22 The element represented by M is different, 0.9 < x2 < 0.98, 0.05 < y2 < 0.20, 0.32 < z2 < 0.40, 0.01 < s2 < 0.07, 0.08 < t2 < 0.22, 0.33 < u2 < 0.40, 0 < a21 + a22 < 0.05, x2 + 2y2 + 3z2 + 3u2 + 2 (a21 + a22) + s2 + 2t2 < 4 < x2 + 2y2 + 4z2 + 3u2 + 4 (a21 + a22) + s2 + 3t2, y2 + z2 + (a21 + a22) + s2 + t2 + u2 = 1, 0 < n < 0.05, -1 < δ < 3.

[0010] Further, the positive electrode material has a general formula of Na x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 (M a31 M a32 M a33 )O 2+nδ , M a31 , M a32 , M a33The elements represented by M are all different, 0.9

[0011] Further, the general formula of the positive electrode material is Na x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 (M a41 M a42 M a43 M a44 M a45 )O 2+nδ , M a41 , M a42 , M a43 , M a44 and M a45 The elements represented by M are all different, 0.9

[0012] Further, the positive electrode material is of O3 type.

[0013] Further, the total amount of residual alkali of the positive electrode material is 1.5-2.2%.

[0014] Further, the total amount of residual alkali of the positive electrode material is 1.78-2.2%.

[0015] Further, the content of sodium carbonate is 1-2.19%, and the content of sodium hydroxide is 0.01-0.5%.

[0016] In a second aspect, the application provides a preparation method of the cathode material, which specifically comprises: taking sodium source and residual metal source according to stoichiometric ratio, mixing the raw materials, drying, performing high-temperature calcination treatment, crushing, and screening to obtain the cathode material.

[0017] In a third aspect, the application provides a sodium ion battery comprising the layered sodium ion battery cathode material.

[0018] Compared with the prior art, the application can achieve at least one of the following beneficial effects:

[0019] (1) The cathode material of the application uses specific ratios of elements, improves the sodium content, increases the proportion of active sodium of the material, and thus the obtained sodium ion battery has high capacity, and the cathode material of the application can keep the residual alkali content within a reasonable range, and the consistency and stability of the battery are good under the high sodium content of the application.

[0020] (2) In the preparation process of the cathode material of the application, a relationship between the calcination temperature and the content of Ni element is established, and under the calcination temperature of the application, the total residual alkali content of the cathode material is 1.5-2.2%, the sodium carbonate content is 1-2.19%, and the sodium hydroxide content is 0.01-0.5%, the battery prepared by using the cathode material of the application has higher capacity, and the electrochemical performance consistency of the battery is good.

[0021] (3) The cathode material of the application does not need to increase the voltage to increase the capacity, and the electrolyte has a wide adaptation range.

[0022] (4) The preparation method of the cathode material of the application is simple, low in cost, and can be mass-produced.

[0023] The above technical solutions can be combined with each other in the application to achieve more preferred combination solutions. Other features and advantages of the application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the application. The purpose and other advantages of the application can be achieved and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings are included to provide a further understanding of the application and are incorporated herein and constitute a part of the application. The drawings illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. In the drawings:

[0025] Figure 1 SEM image of the cathode material prepared for Example 1 of the application;

[0026] Figure 2SEM image of the positive electrode material prepared for Example 7 of the present application. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present application will be described in detail with reference to the drawings, in which the figures form a part of the description and are illustrative of the principles of the application, and are not intended to limit the scope of the application.

[0028] In one specific embodiment of the present application, a layered sodium ion battery positive electrode material is disclosed, the general formula of the positive electrode material is Na x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 M a2 O 2+nδ ;

[0029] 0.9 < x2 < 0.98, 0.05 < y2 < 0.20, 0.32 < z2 < 0.40, 0.01 < s2 < 0.07, 0.08 < t2 < 0.22, 0.33 < u2 < 0.40, 0 < a2 < 0.05, 0.34 (y2 + z2 + t2 + u2) < u2 / x2 < 0.51 (y2 + z2 + t2 + u2), x2 + 2y2 + 3z2 + 3u2 + 2a2 + s2 + 2t2 < 4 < x2 + 2y2 + 4z2 + 3u2 + 4a2 + s2 + 3t2, y2 + z2 + a2 + s2 + t2 + u2 = 1, 0 < n < 0.05, -1 < δ < 3;

[0030] The M is one or more of Mg, Ca, B, Al, Li, K, Ag, Zr, Ti, W, Mo, Cr, Sr, Y, Cd, Sn, Sb, Ce.

[0031] Compared with the prior art, the specific ratio of each element in the positive electrode material of the present application improves the sodium content, increases the proportion of active sodium of the positive electrode material, and thus the obtained sodium ion battery has a higher capacity, and the positive electrode material of the present application can keep the residual alkali content within a reasonable range, and the consistency and stability of the battery are good under the higher sodium content of the present application.

[0032] It should be noted that too high Na content and too high residual alkali content, too low capacity, too high Cu content and high impurities, too low air stability, too high Mn content and serious electrolyte decomposition, unstable structure, too low Li content and poor rate, unstable structure, too high Ni content and low working voltage, too low cycle, too high Fe content and serious high-pressure migration of elements, too low capacity, M is only an additive, too high impact on capacity, and too low no improvement.

[0033] Another embodiment of the present application specifically discloses a positive electrode material of the formula Na x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 (M a21 M a22 )O 2+nδ , M a21 , M a22 , and M x2 , wherein the elements represented by M are different, 0.9 < x2 ≤ 0.98, 0.05 ≤ y2 ≤ 0.20, 0.32 ≤ z2 ≤ 0.40, 0.01 ≤ s2 ≤ 0.07, 0.08 ≤ t2 ≤ 0.22, 0.33 ≤ u2 ≤ 0.40, 0 ≤ a21 + a22 ≤ 0.05, x2 + 2y2 + 3z2 + 3u2 + 2(a21 + a22) + s2 + 2t2 < 4 < x2 + 2y2 + 4z2 + 3u2 + 4(a21 + a22) + s2 + 3t2, y2 + z2 + (a21 + a22) + s2 + t2 + u2 = 1, 0 < n ≤ 0.05, -1 ≤ δ ≤ 3.

[0034] Another embodiment of the present application specifically discloses a positive electrode material of the formula Na y2 Cu z2 Mn s2 Li t2 Ni u2 Fe a31 (M a32 M a33 M 2+nδ )O a31 , M a32 , M a33 , and M x2 , wherein the elements represented by M are different, 0.9 < x2 ≤ 0.98, 0.05 ≤ y2 ≤ 0.20, 0.32 ≤ z2 ≤ 0.40, 0.01 ≤ s2 ≤ 0.07, 0.08 ≤ t2 ≤ 0.22, 0.33 ≤ u2 ≤ 0.40, 0 ≤ a31 + a32 + a33 ≤ 0.05, x2 + 2y2 + 3z2 + 3u2 + 2(a31 + a32 + a33) + s2 + 2t2 < 4 < x2 + 2y2 + 4z2 + 3u2 + 4(a31 + a32 + a33) + s2 + 3t2, y2 + z2 + (a31 + a32 + a33) + s2 + t2 + u2 = 1, 0 < n ≤ 0.05, -1 ≤ δ ≤ 3.

[0035] Another embodiment of the present application specifically discloses a positive electrode material of the formula Na y2 Cu z2Li s2 Ni t2 Fe u2 (M a41 M a42 M a43 M a44 M a45 )O 2+nδ M a41 M a42 M a43 M a44 and M a45 In the given equation, M represents different elements, where 0.9 < x² ≤ 0.98, 0.05 ≤ y² ≤ 0.20, 0.32 ≤ z² ≤ 0.40, 0.01 ≤ s² ≤ 0.07, 0.08 ≤ t² ≤ 0.22, 0.33 ≤ u² ≤ 0.40, 0 ≤ a₄₁ + a₄₂ + a₄₃ + a₄₄ + a₄₅ ≤ 0.05, and x² + 2y² + 3z² + 3u² +2(a41+a42+a43+a44+a45)+s2+2t2<4<x2+2y2+4z2+3u2+4(a41+a42+a43+a44+ a45)+s2+3t2, y2+z2+(a41+a42+a43+a44+a45)+s2+t2+u2=1, 0<n≤0.05, -1≤δ≤3.

[0036] Specifically, the cathode material is of the O3 type.

[0037] Specifically, the total residual alkali of the cathode material is 1.5-2.2%, for example, 1.5%, 1.6%, 1.7%, 1.76%, 1.8%, 1.9%, 2.01%, 2.1%, and 2.2%.

[0038] In a preferred embodiment, the total residual alkali of the cathode material is 1.78-2.2%.

[0039] Specifically, the sodium carbonate content is 1-2.19%, for example, 1%, 1.2%, 1.4%, 1.6%, 1.76%, 1.8%, 2.01%, 2.1%, and 2.19%, and the sodium hydroxide content is 0.01-0.5%, for example, 0.01%, 0.019%, 0.05%, 0.10%, 0.15%, 0.12%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, and 0.5%.

[0040] In the preferred embodiment, the sodium carbonate content is 1.76-2.01%, and the sodium hydroxide content is 0.019-0.12%.

[0041] Another specific embodiment of the present invention discloses a method for preparing the cathode material, which is as follows: according to the stoichiometric ratio, sodium source and residual metal source are weighed, the raw materials are mixed, dried, subjected to high-temperature calcination, crushed, and sieved to obtain the cathode material.

[0042] Specifically, the high-temperature calcination temperature is (800+400t2)~1050℃, and the calcination time is 8-24h, for example, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h.

[0043] In the preparation of the cathode material of this invention, a relationship between calcination temperature and Ni element content was established. Using the calcination temperature of this invention, the total residual alkali content of the cathode material can be 1.5-2.2%, the sodium carbonate content can be 1-2.19%, and the sodium hydroxide content can be 0.01-0.5%.

[0044] Specifically, the heating rate during high-temperature calcination is 1-5℃ / min, for example, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min.

[0045] Specifically, the high-temperature calcination atmosphere is air or oxygen.

[0046] Another embodiment of the present invention discloses a sodium-ion battery, including the aforementioned layered sodium-ion battery cathode material.

[0047] Compared with the prior art, the sodium-ion battery of the present invention has a higher proportion of active sodium, which improves the capacity of the sodium-ion battery, and has lower requirements for electrolyte, resulting in better battery stability.

[0048] It should be noted that the battery consistency mentioned in this invention refers to selecting three batteries with the maximum, minimum and median values ​​from the same batch of batteries during the testing process, and comparing their capacity differences, as detailed in Table 1. If the three batteries have similar capacities at the same rate and different rates, then the consistency is good.

[0049] The following specific embodiments will be used to explain the cathode material described in this invention.

[0050] Example 1

[0051] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.12 Mn 0.37 Ni 0.1 Fe 0.36 Li 0.04 Al 0.01The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, Al2O3 and MnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B2.

[0052] Example 2

[0053] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.12 Mn 0.37 Ni 0.1 Fe 0.36 Li 0.04 Al 0.01 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, Al2O3 and MnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 840℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B2-1.

[0054] Example 2-1

[0055] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.12 Mn 0.32 Ni 0.1 Fe 0.37 Li 0.04 Ti 0.05 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, MnO2 and TiO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B2-3.

[0056] Example 2-2

[0057] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.12 Mn 0.35 Ni 0.1 Fe 0.37 Li 0.04 Zr 0.02The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, MnO2 and ZrO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B2-4.

[0058] Example 2-3

[0059] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.12 Mn 0.36 Ni 0.1 Fe 0.37 Li 0.04 Sn 0.01 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, MnO2 and SnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B2-5.

[0060] Examples 2-4

[0061] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.12 Mn 0.36 Ni 0.1 Fe 0.37 Li 0.04 Ce 0.01 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, MnO2 and CeO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained, denoted as B2-6.

[0062] Examples 2-5

[0063] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.09 Mn 0.37 Ni 0.1 Fe 0.37 Li 0.04 Mg 0.03The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, MnO2 and Mg(OH)2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained, denoted as B2-7.

[0064] Examples 2-6

[0065] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.10 Mn 0.37 Ni 0.1 Fe 0.37 Li 0.04 Ca 0.02 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, MnO2 and CaO are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained, denoted as B2-8.

[0066] Examples 2-7

[0067] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.10 Mn 0.37 Ni 0.08 Fe 0.37 Li 0.04 B 0.02 K 0.02 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, B2O3, MnO2 and K2CO3 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B2-9.

[0068] Examples 2-8

[0069] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.10 Mn 0.36 Ni 0.09 Fe 0.37 Li 0.04 Ag 0.02 W 0.01 Sr 0.01The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, Ag2O, WO3, MnO2 and SrCO3 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained, denoted as B2-10.

[0070] Examples 2-9

[0071] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.11 Mn 0.33 Ni 0.10 Fe 0.37 Li 0.04 Y 0.01 Mo 0.01 Cr 0.01 Cd 0.01 Sb 0.01 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, Y2O3, MoO3, CdO, Cr2O3, MnO2 and Sb2O3 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained, denoted as B2-11.

[0072] Example 3

[0073] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.98 Cu 0.12 Mn 0.37 Ni 0.1 Fe 0.36 Li 0.04 Al 0.01 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, Al2O3 and MnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 1050℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained, denoted as B2-2.

[0074] Example 4

[0075] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.94 Cu 0.05 Mn 0.4 Ni 0.1 Fe0.33 Li 0.07 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2 and MnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature for 16 hours in a compressed oxygen atmosphere at 910℃ with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B6.

[0076] Example 5

[0077] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.95 Cu 0.18 Mn 0.33 Ni 0.08 Fe 0.40 Li 0.01 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2 and MnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 980℃ for 16h with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B7.

[0078] Example 6

[0079] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.95 Cu 0.05 Mn 0.34 Ni 0.22 Fe 0.33 Li 0.01 Al 0.05 The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2, Al2O3 and MnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 960℃ for 16h, with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B8.

[0080] Example 7

[0081] In this embodiment, the layered sodium-ion battery cathode material is of the O3 type, with the general formula Na. 0.92 Cu 0.2 Mn 0.38 Ni 0.08 Fe 0.33 Li 0.01The specific preparation method of O2 is as follows: Na2CO3, CuO, Fe2O3, Li2CO3, Ni(OH)2 and MnO2 are weighed according to the stoichiometric ratio, mixed evenly, dried, and calcined at high temperature in compressed air atmosphere at 910℃ for 16h with a heating rate of 2℃ / min. After crushing and sieving, the positive electrode material is obtained and denoted as B9.

[0082] Comparative Example 1

[0083] One of the cathode materials in this comparative example is of the O3 type, with the general formula Na. 0.9 Cu 0.12 Mn 0.37 Ni 0.1 Fe 0.36 Li 0.04 Al 0.01 O2 was prepared using the same method as in Example 1, resulting in the cathode material described above, denoted as A2.

[0084] Comparative Example 2

[0085] One of the cathode materials in this comparative example is of the O3 type, with the general formula Na. 0.99 Cu 0.12 Mn 0.37 Ni 0.1 Fe 0.36 Li 0.04 Al 0.01 O2 was prepared using the same method as in Example 1, resulting in the cathode material described above, denoted as A4.

[0086] Comparative Example 3

[0087] The layered sodium-ion battery cathode material in this comparative example is of type O3. The general formula and preparation method are the same as those in Example 1, except that the high-temperature calcination temperature is 830°C to obtain the cathode material, which is denoted as C1.

[0088] Comparative Example 4

[0089] The layered sodium-ion battery cathode material in this comparative example is of type O3. The general formula and preparation method are the same as those in Example 1, except that the high-temperature calcination temperature is 1060℃ to obtain the cathode material, which is denoted as C2.

[0090] Experimental Example 1

[0091] Battery assembly: The positive electrode materials of Examples 1-7 and Comparative Examples 1-4 were used as active materials, mixed at a mass ratio of 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. A sodium metal sheet was used as the counter electrode, Waterman glass fiber as the separator, and 1 mol / L NaPF6EC / DMC = 1:1 (Alfa) as the electrolyte. 2032 coin cells were assembled in an Ar protective glove box.

[0092] (1) The battery was tested in the voltage range of 2.5 to 4.0V, activated at 0.1C for three weeks, and cycled at 1C for three weeks. The specific capacity of the battery in the first week of discharge at 0.1C, the first discharge specific capacity at 0.5C, and the first discharge specific capacity at 1C were recorded. The results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As can be seen from Table 1, the 0.1C, 0.5C, and 1C capacities of A2, A4, C1, and C2 are significantly different and relatively low; while the 0.1C, 0.5C, and 1C capacities of B2 to B2-11 and B6 to B9 are basically at a similar level and the consistency of the three batteries is good.

[0096] Compared to A2, A4, and B2, the 0.1C capacity is increased by more than 10 mAh / g. A2 is sodium-poor, A4 is sodium-excessive, and B2 is sodium-rich. B2 has superior rate performance and very stable capacity, indicating that only by using the Na content of this invention can the battery capacity be stabilized.

[0097] Based on the above analysis, it can be seen that only cathode materials prepared within the Na content range of the present invention exhibit excellent performance.

[0098] (2) The total residual alkali of Examples 1-7 and Comparative Examples 1-4 were tested. The results are shown in Table 2. The total residual alkali (i.e., mass ratio) = mass ratio of sodium carbonate + mass ratio of sodium hydroxide.

[0099] Residual alkali content test: obtained by Metrohm 888 / 905 instrument.

[0100] Table 2

[0101] Materials Mass ratio (sodium carbonate + sodium hydroxide) / % Mass ratio (sodium carbonate) / % Mass ratio (sodium hydroxide) / % B2 1.815 1.790 0.025 B2-1 2.121 2.010 0.111 B2-2 1.952 1.907 0.045 B2-3 1.814 1.792 0.022 B2-4 1.816 1.793 0.023 B2-5 1.815 1.791 0.024 B2-6 1.817 1.790 0.027 B2-7 1.812 1.791 0.021 B2-8 1.814 1.795 0.019 B2-9 1.816 1.792 0.024 B2-10 1.815 1.794 0.021 B2-11 1.818 1.796 0.022 B6 1.834 1.810 0.024 B7 1.802 1.780 0.022 B8 1.823 1.800 0.023 B9 1.781 1.760 0.021 A2 1.781 1.760 0.021 A4 2.721 2.630 0.091 C1 2.442 2.231 0.211 C2 2.231 2.198 0.033

[0102] As can be seen from Tables 1 and 2, compared with B2, A2 has a lower total alkali content but its capacity is difficult to achieve. A4 has a higher total alkali content, and its sodium carbonate and sodium hydroxide content are also higher, resulting in poorer electrical performance. This indicates that only the cathode material prepared using the element ratio of the present invention has not only a higher capacity but also a lower residual alkali content.

[0103] Furthermore, compared to C1 and C2, B2, B2-1, and B2-2 only change the sintering temperature. When the temperature is below 840°C, the battery capacity is low and the sodium carbonate content is high. When the temperature is above 1050°C, although the battery capacity is improved, the battery consistency is poor. Only at the sintering temperature specified in this invention are the battery capacity, residual alkali content, and battery consistency all better.

[0104] (3) The SEM images of materials B2 and B9 are shown below. Figure 1 and 2 As shown in the figure, the large particles of the measured material are uniformly covered with small particles, which represents the residual alkali content, indicating that the material surface is rich in sodium.

[0105] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A layered sodium-ion battery cathode material, characterized in that, The general formula of the cathode material is Na. x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 M a2 O 2+nδ ; Among them, 0.9 < x2<0.51(y2+z2+t2+u2), x2+2y2+3z2+3u2+2a2+s2+2t2<4<x2+2y2 +4z2+3u2+4a2+s2+3t2, y2+z2+a2+s2+t2+u2=1, 0<n≤0.05, -1≤δ≤3; M is one or more of Mg, Ca, B, Al, Li, K, Ag, Zr, Ti, W, Mo, Cr, Sr, Y, Cd, Sn, Sb, and Ce; The total residual alkali content of the cathode material is 1.5-2.2%, the sodium carbonate content is 1-2.19%, and the sodium hydroxide content is 0.01-0.5%.

2. The layered sodium-ion battery cathode material according to claim 1, characterized in that, The general formula of the cathode material is Na. x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 (M a21 M a22 )O 2+nδ M a21 and M a22 In the equation, M represents different elements: 0.9 < x² ≤ 0.98, 0.05 ≤ y² ≤ 0.20, 0.32 ≤ z² ≤ 0.37, 0.01 ≤ s² ≤ 0.07, 0.08 ≤ t² ≤ 0.1, 0.33 ≤ u² ≤ 0.37, 0 ≤ a²¹ + a²² ≤ 0.05, x² + 2y² + 3z² + 3u² + 2(a²¹ + a²²) + s² + 2t² < 4 < x² + 2y² + 4z² + 3u² + 4(a²¹ + a²²) + s² + 3t², y² + z² + (a²¹ + a²²) + s² + t² + u² = 1, 0 < n ≤ 0.05, -1 ≤ δ ≤ 3.

3. The layered sodium-ion battery cathode material according to claim 1, characterized in that, The general formula of the cathode material is Na. x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 (M a31 M a32 M a33 )O 2+nδ M a31 M a32 and M a33 In the equation, M represents different elements: 0.9 < x² ≤ 0.98, 0.05 ≤ y² ≤ 0.20, 0.32 ≤ z² ≤ 0.37, 0.01 ≤ s² ≤ 0.07, 0.08 ≤ t² ≤ 0.1, 0.33 ≤ u² ≤ 0.37, 0 ≤ a³¹ + a³² + a³³ ≤ 0.05, x² + 2y² + 3z² + 3u² + 2(a³¹ + a³² + a³³) + s² + 2t² < 4 < x² + 2y² + 4z² + 3u² + 4(a³¹ + a³² + a³³) + s² + 3t², y² + z² + (a³¹ + a³² + a³³) + s² + t² + u² = 1, 0 < n ≤ 0.05, -1 ≤ δ ≤ 3.

4. The layered sodium-ion battery cathode material according to claim 1, characterized in that, The general formula of the cathode material is Na. x2 Cu y2 Mn z2 Li s2 Ni t2 Fe u2 (M a41 M a42 M a43 M a44 M a45 )O 2+nδ M a41 M a42 M a43 M a44 and M a45 In the given equation, M represents different elements: 0.9 < x² ≤ 0.98, 0.05 ≤ y² ≤ 0.20, 0.32 ≤ z² ≤ 0.37, 0.01 ≤ s² ≤ 0.07, 0.08 ≤ t² ≤ 0.1, 0.33 ≤ u² ≤ 0.37, 0 ≤ a₄¹ + a₄² + a₄³ + a₄₄ + a₄₅ ≤ 0.05, x² + 2y² + 3z² + 3u² + 2 (a41+a42+a43+a44+a45)+s2+2t2<4<x2+2y2+4z2+3u2+4(a41+a42+a43+a44+a 45)+s2+3t2, y2+z2+(a41+a42+a43+a44+a45)+s2+t2+u2=1, 0<n≤0.05, -1≤δ≤3.

5. A layered sodium-ion battery cathode material according to any one of claims 1-4, characterized in that, The positive electrode material is of type O3.

6. The layered sodium-ion battery cathode material according to claim 1, characterized in that, The total residual alkali content of the cathode material is 1.78-2.2%.

7. A method for preparing a layered sodium-ion battery cathode material according to any one of claims 1-6, characterized in that, Specifically, the sodium source and the remaining metal source are weighed according to the stoichiometric ratio, the raw materials are mixed, dried, and subjected to high-temperature calcination treatment, wherein the high-temperature calcination temperature is (800+400t2)~1050℃, crushed, and sieved to obtain the cathode material.

8. A sodium-ion battery, characterized in that, This includes the cathode material as described in any one of claims 1-6 or the cathode material prepared by the method of claim 7.

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