Preparation method of sodium-rich low-residual-alkali layered oxide positive electrode material

Abstract

The application relates to a preparation method of a sodium-rich low-residual-alkali layered oxide positive electrode material, and belongs to the technical field of sodium ion batteries, to solve the problems that the residual alkali content of the positive electrode material prepared by the existing method is high due to high sodium content, and the capacity and other performances of the sodium ion battery are affected. In the method, specific proportions of various elements are adopted, the sodium content is improved, the proportion of active sodium of the material is improved, and the obtained sodium ion battery has high capacity. The positive electrode material 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.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a method for preparing a layered oxide cathode material rich in sodium and low in residual alkali. Background Technology

[0002] Sodium-ion batteries have relatively low energy density. Although layered oxide cathode materials have a high theoretical capacity, their actual capacity is limited. Introducing other elements after product finalization is not feasible, and adjusting the proportions involves the entire subsequent new product development process. Furthermore, electrolytes are difficult to adapt to higher voltages. Therefore, finding ways to improve capacity within the existing voltage range using current processes is crucial.

[0003] Existing methods for improving electrolyte capacity mainly include improving the structure by doping existing elements at higher voltages, adjusting the proportions, and trying new materials. However, current electrolyte systems are difficult to adapt to higher voltages, and elemental doping improvement requires the introduction of other elements, which is difficult to implement on existing production lines. After adjusting the proportions, the various properties of the material need to be re-evaluated, and subsequent system development must be completely restarted, which is time-consuming and labor-intensive. The development of new materials is also difficult, and it is difficult to balance production processes.

[0004] Excessive sodium content leads to high alkalinity in the material, and high residual alkali content causes the cell slurry to easily gel, resulting in gas generation during cell charging and discharging. High-nickel materials may even require water washing, multi-layer coating, and multi-element doping to reduce residual alkali content. However, there is a direct linear relationship between the theoretical capacity of the material and the molar ratio of Na. The amount of sodium content has some influence on the material's capacity utilization, and higher sodium content can improve the material's consistency and stability. Current methods for preparing cathode materials cannot simultaneously meet the requirements of being sodium-rich and having low residual alkali content. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method for preparing a layered oxide cathode material rich in sodium and with low residual alkali content, in order to solve the problem that existing methods for preparing cathode materials with high sodium content result in high residual alkali content, which in turn affects the capacity and other performance of sodium-ion batteries.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a sodium-rich, low-residue layered oxide cathode material includes the following steps:

[0008] (1) Weigh out each metal source as raw material according to the molar ratio: 1<Na≤1.1, 0.05≤Cu≤0.20, 0.33≤Mn≤0.40, 0.20≤Ni≤0.24, 0.33≤Fe≤0.40, 0≤M≤0.05;

[0009] (2) Mix the prepared raw materials, dry them, calcine them at high temperature, crush them, and sieve them to obtain the positive electrode material;

[0010] Wherein, 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.

[0011] Furthermore, in step (2), the high-temperature calcination temperature is (800+400t3)~1050℃, and the calcination time is 8-24h, where t3 is the molar ratio of Ni element.

[0012] Furthermore, in step (2), the heating rate during high-temperature calcination is 1-5℃ / min.

[0013] Furthermore, in step (2), the high-temperature calcination atmosphere is air or oxygen.

[0014] Furthermore, the general formula of the cathode material is Na. x3 Cu y3 Mn z3 Ni t3 Fe u3 M a3 O 2+nδ ; Among them, 1<x3≤1.1, 0.05≤y3≤0.20, 0.33≤z3≤0.40, 0.20≤t3≤0.24, 0.33≤u3≤ 0.40, 0≤a3≤0.05, 0.34(y3+z3+t3+u3)<u3 / x3<0.51(y3+z3+t3+u3) and 0.1 8(y3+z3+t3+u3)<t3 / x3<0.25(y3+z3+t3+u3), x3+2y3+3z3+3u3+2a3+3t 3<4<x3+2y3+4z3+3u3+4a3+3t3, y3+z3+a3+t3+u3=1, 0<n≤0.05, -1≤δ≤3.

[0015] Furthermore, the general formula of the cathode material is Na. x3 Cu y3 Mn z3 Ni t3 Fe u3 (M a31 M a32 )O 2+nδ M a31 and M a32In the equation, M represents different elements, where 1 < x³ ≤ 1.1, 0.05 ≤ y³ ≤ 0.20, 0.33 ≤ z³ ≤ 0.40, 0.20 ≤ t³ ≤ 0.24, 0.33 ≤ u³ ≤ 0.40, 0 ≤ a³¹ + a³² ≤ 0.05, 0.34(y³ + z³ + t³ + u³) < u³ / x³ < 0.51(y³ + z³ + t³ + u³) and 0.18(y 3+z3+t3+u3)<t3 / x3<0.25(y3+z3+t3+u3), x3+2y3+3z3+3u3+2(a31+a32)+3t3<4<x 3+2y3+4z3+3u3+4(a31+a32)+3t3, y3+z3+(a31+a32)+t3+u3=1, 0<n≤0.05, -1≤δ≤3.

[0016] Furthermore, the general formula of the cathode material is Na. x3 Cu y3 Mn z3 Ni t3 Fe u3

[0017] (M a41 M a42 M a43 )O 2+nδ M a41 M a42 and M a43 In the equation, M represents different elements, where 1 < x³ ≤ 1.1, 0.05 ≤ y³ ≤ 0.20, 0.33 ≤ z³ ≤ 0.40, 0.20 ≤ t³ ≤ 0.24, 0.33 ≤ u³ ≤ 0.40, 0 ≤ a₄¹ + a₄² + a₄³ ≤ 0.05, and 0.34(y³ + z³ + t³ + u³) < u³ / x³ < 0.51

[0018] (y3+z3+t3+u3) and 0.18(y3+z3+t3+u3)<t3 / x3<0.25(y3+z3+t3+u3), x3+2y3+3z3+3u3+2(a41+a42+a43)+3t3<4<x3+2y3+4z3+3u3+4

[0019] (a41+a42+a43)+3t3, y3+z3+(a41+a42+a43)+t3+u3=1, 0<n≤0.05, -1≤δ≤3.

[0020] Furthermore, the positive electrode material is of the O3 type.

[0021] Furthermore, the total residual alkali content of the cathode material is 1.5-2.2%.

[0022] Furthermore, the sodium carbonate content is 1-2.19%, and the sodium hydroxide content is 0.01-0.5%.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] (1) The method of the present invention uses a specific ratio of each element, which increases the amount of sodium and the proportion of active sodium in the material, thereby the sodium-ion battery obtained has a high capacity. The positive electrode material of the present invention can keep the residual alkali within a reasonable range. Under the high sodium content of the present invention, the battery has good consistency and stability.

[0025] (2) In the preparation method of the present invention, a relationship between calcination temperature and Ni element content is constructed. Under the calcination temperature of the present invention, the total residual alkali of the cathode material can be 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 using the cathode material of the present invention has a higher capacity and better consistency in electrochemical performance.

[0026] (3) The positive electrode material prepared by the method of the present invention does not require increasing the voltage to increase the capacity, and the electrolyte has a wide range of compatibility.

[0027] (4) The preparation method of the positive electrode material of the present invention is simple, low in cost, and can be mass-produced.

[0028] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0029] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0030] Figure 1 This is a SEM image of the cathode material of Example 1 of the present invention;

[0031] Figure 2 This is a SEM image of the cathode material in Example 2 of the present invention. Detailed Implementation

[0032] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0033] A specific embodiment of the present invention discloses a method for preparing a sodium-rich, low-alkali-residue layered oxide cathode material, comprising the following steps:

[0034] (1) Weigh out each metal source as raw material according to the molar ratio: 1<Na≤1.1, 0.05≤Cu≤0.20, 0.33≤Mn≤0.40, 0.20≤Ni≤0.24, 0.33≤Fe≤0.40, 0≤M≤0.05;

[0035] (2) Mix the prepared raw materials, dry them, calcine them at high temperature, crush them, and sieve them to obtain the cathode material;

[0036] Wherein, 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.

[0037] Compared with the prior art, the method of the present invention uses a specific ratio of each element, which increases the amount of sodium and the proportion of active sodium in the material, while the residual alkali content can be kept within a reasonable range, thus resulting in a sodium-ion battery with high capacity.

[0038] It should be noted that excessive Na content results in excessive residual alkali, while excessively low Na content results in low capacity; excessive Cu content makes it difficult to dissolve solids and results in high impurities, while excessively low Cu content leads to poor air stability; excessive Mn content results in poor cycling and severe electrolyte decomposition, while excessively low Mn content leads to structural instability; excessive Ni content results in low operating voltage, while excessively low Ni content results in poor cycling; excessive Fe content results in poor cycling and severe high-voltage migration of elements, while excessively low Fe content leads to low capacity; M is only an additive, excessively high Mn content affects capacity, while excessively low Mn content does not improve capacity.

[0039] Specifically, in step (2), the high-temperature calcination temperature is (800+400t3)~1050℃, and the calcination time is 8-24h, where t3 is the molar ratio of Ni element.

[0040] In the preparation process of the cathode material of the present invention, a relationship between calcination temperature and Ni element content was established. At the calcination temperature of the present invention, the total residual alkali 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%. The battery prepared using the cathode material of the present invention has a higher capacity and better consistency in electrochemical performance.

[0041] Specifically, in step (2), the heating rate during high-temperature calcination is 1-5℃ / min, for example, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min.

[0042] Specifically, in step (2), the high-temperature calcination atmosphere is air or oxygen.

[0043] A specific embodiment of the present invention discloses a cathode material of the general formula Na prepared by the method of the present invention. x3 Cu y3 Mn z3 Ni t3 Fe u3 M a3 O 2+nδ ; Among them, 1<x3≤1.1, 0.05≤y3≤0.20, 0.33≤z3≤0.40, 0.20≤t3≤0.24, 0.33≤u3≤ 0.40, 0≤a3≤0.05, 0.34(y3+z3+t3+u3)<u3 / x3<0.51(y3+z3+t3+u3) and 0.1 8(y3+z3+t3+u3)<t3 / x3<0.25(y3+z3+t3+u3), x3+2y3+3z3+3u3+2a3+3t 3<4<x3+2y3+4z3+3u3+4a3+3t3, y3+z3+a3+t3+u3=1, 0<n≤0.05, -1≤δ≤3.

[0044] A specific embodiment of the present invention discloses a cathode material of the general formula Na prepared by the method of the present invention. x3 Cu y3 Mn z3 Ni t3 Fe u3 (M a31 M a32 )O 2+nδ M a31 and M a32 In the equation, M represents different elements, where 1 < x³ ≤ 1.1, 0.05 ≤ y³ ≤ 0.20, 0.33 ≤ z³ ≤ 0.40, 0.20 ≤ t³ ≤ 0.24, 0.33 ≤ u³ ≤ 0.40, 0 ≤ a³¹ + a³² ≤ 0.05, 0.34(y³ + z³ + t³ + u³) < u³ / x³ < 0.51(y³ + z³ + t³ + u³) and 0.18(y 3+z3+t3+u3)<t3 / x3<0.25(y3+z3+t3+u3), x3+2y3+3z3+3u3+2(a31+a32)+3t3<4<x 3+2y3+4z3+3u3+4(a31+a32)+3t3, y3+z3+(a31+a32)+t3+u3=1, 0<n≤0.05, -1≤δ≤3.

[0045] A specific embodiment of the present invention discloses a cathode material of the general formula Na prepared by the method of the present invention. x3 Cu y3 Mn z3 Nit3 Fe u3 (M a41 M a42 M a43 )O 2+nδ M a41 M a42 and M a43 In the given equation, M represents different elements, where 1 < x³ ≤ 1.1, 0.05 ≤ y³ ≤ 0.20, 0.33 ≤ z³ ≤ 0.40, 0.20 ≤ t³ ≤ 0.24, 0.33 ≤ u³ ≤ 0.40, 0 ≤ a₄¹ + a₄² + a₄³ ≤ 0.05, 0.34(y³ + z³ + t³ + u³) < u³ / x³ < 0.51(y³ + z³ + t³ + u³) and 0.18(y³ + z³) +t3+u3)<t3 / x3<0.25(y3+z3+t3+u3), x3+2y3+3z3+3u3+2(a41+a42+a43)+3t3<4<x3+2y 3+4z3+3u3+4(a41+a42+a43)+3t3, y3+z3+(a41+a42+a43)+t3+u3=1, 0<n≤0.05, -1≤δ≤3.

[0046] Specifically, the cathode material is of the O3 type.

[0047] Specifically, the total residual alkali of the cathode material is 1.5-2.2%, for example, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1.99%, 2.04%, 2.1%, and 2.2%.

[0048] In a preferred embodiment, the total residual alkali content of the cathode material is 1.99-2.04%.

[0049] 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%.

[0050] In the preferred embodiment, the sodium carbonate content is 1.95-2.01%, and the sodium hydroxide content is 0.025-0.040%.

[0051] In another embodiment, the present invention discloses a sodium-ion battery comprising the aforementioned positive electrode material.

[0052] 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.

[0053] 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.

[0054] The following specific embodiments will be used to explain the cathode material described in this invention.

[0055] Example 1

[0056] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0057] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, ZrO2 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.11, Mn0.33, Ni0.22, Fe0.33, Zr0.01;

[0058] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, which is denoted as B3.

[0059] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0060] Na 1.1 Cu 0.11 Mn 0.33 Ni 0.22 Fe 0.33 Zr 0.01 O2.

[0061] Example 1-1

[0062] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0063] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, TiO2 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.22, Fe0.33, Ti0.02;

[0064] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-1.

[0065] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0066] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.22 Fe 0.33 Ti 0.02 O2.

[0067] Examples 1-2

[0068] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0069] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, B2O3, Al2O3 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.1, Mn0.33, Ni0.21, Fe0.33, Al0.02, B0.01;

[0070] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-2.

[0071] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0072] Na 1.1 Cu 0.1 Mn 0.33 Ni 0.21 Fe 0.33 Al 0.02 B 0.01 O2.

[0073] Examples 1-3

[0074] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0075] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, Mg(OH)2 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.20, Fe0.33, Mg0.05;

[0076] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-3.

[0077] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0078] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.20 Fe 0.33 Mg 0.05 O2.

[0079] Examples 1-4

[0080] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0081] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, CaO, Li2CO3, SnO2 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.20, Fe0.33, Ca0.01, Li0.02 and Sn0.02;

[0082] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-4.

[0083] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0084] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.20 Fe 0.33 Ca 0.01 Li 0.02 Sn 0.02 O2.

[0085] Examples 1-5

[0086] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0087] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, Ag2O, WO3, CeO2 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.20, Fe0.33, W0.01, Ag0.02 and Ce0.02;

[0088] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-5.

[0089] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0090] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.20 Fe 0.33 W 0.01 Ag 0.02 Ce 0.02 O2.

[0091] Examples 1-6

[0092] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0093] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, Al2O3, SrCO3, Y2O3 and MnO2 as raw materials according to the molar ratio: Na 1.1, Cu 0.10, Mn 0.33, Ni 0.21, Fe 0.33, Sr 0.01, Y 0.01 and Al 0.01;

[0094] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-6.

[0095] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0096] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.21 Fe 0.33 Sr 0.01 Y 0.01 Al 0.01 O2.

[0097] Examples 1-7

[0098] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0099] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, Mo2O3, Sb2O3 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.22, Fe0.33, Mo0.01, Sb0.01;

[0100] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-7.

[0101] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0102] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.22 Fe 0.33 Mo 0.01 Sb 0.01 O2.

[0103] Examples 1-8

[0104] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0105] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, Sb2O3 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.22, Fe0.33, Sb0.02;

[0106] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-8.

[0107] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0108] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.22 Fe 0.33 Sb 0.02 O2.

[0109] Examples 1-9

[0110] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0111] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, CdO and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.22, Fe0.33, Cd0.02;

[0112] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-9.

[0113] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0114] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.22 Fe 0.33 Cd 0.02 O2.

[0115] Examples 1-10

[0116] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0117] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, Cr2O3 and MnO2 as raw materials according to the molar ratio: Na1.1, Cu0.10, Mn0.33, Ni0.22, Fe0.33, Cr0.02;

[0118] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B3-10.

[0119] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0120] Na 1.1 Cu 0.10 Mn 0.33 Ni 0.22 Fe 0.33 Cr 0.02 O2.

[0121] Example 2

[0122] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0123] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2 and MnO2 as raw materials according to the molar ratio: Na 1.01, Cu 0.1, Mn 0.33, Ni 0.24, Fe 0.33;

[0124] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 24 hours in a compressed oxygen atmosphere at 1000℃ with a heating rate of 2℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B10.

[0125] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0126] Na 1.01 Cu 0.1 Mn 0.33 Ni 0.24 Fe 0.33 O2.

[0127] Example 3

[0128] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0129] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, K2CO3 and MnO2 as raw materials according to the molar ratio: Na 1.01, Cu 0.05, Mn 0.33, Ni 0.21, Fe 0.37, K 0.04;

[0130] (2) Mix the prepared raw materials evenly, dry them, and calcine them at a high temperature of 970℃ in compressed air atmosphere for 24h with a heating rate of 2℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B11.

[0131] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0132] Na 1.01 Cu 0.05 Mn 0.33 Ni 0.21 Fe 0.37 K 0.04 O2.

[0133] Example 4

[0134] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0135] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, K2CO3 and MnO2 as raw materials according to the molar ratio: Na 1.01, Cu 0.05, Mn 0.37, Ni 0.2, Fe 0.33, K 0.05;

[0136] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature in compressed air atmosphere at 960℃ for 24h, with a heating rate of 2℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B12.

[0137] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0138] Na 1.01 Cu 0.05 Mn 0.37 Ni 0.2 Fe 0.33 K 0.05 O2.

[0139] Example 5

[0140] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0141] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, K2CO3 and MnO2 as raw materials according to the molar ratio: Na 1.01, Cu 0.05, Mn 0.37, Ni 0.2, Fe 0.33, K 0.05;

[0142] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature in compressed air atmosphere at 880℃ for 24h with a heating rate of 2℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B12-1.

[0143] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0144] Na 1.01 Cu 0.05 Mn 0.37 Ni 0.2 Fe 0.33 K 0.05 O2.

[0145] Example 6

[0146] This embodiment describes a method for preparing a sodium-rich, low-residue layered oxide cathode material, comprising the following steps:

[0147] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, K2CO3 and MnO2 as raw materials according to the molar ratio: Na 1.01, Cu 0.05, Mn 0.37, Ni 0.2, Fe 0.33, K 0.05;

[0148] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature in compressed air atmosphere at 1050℃ for 24h with a heating rate of 2℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as B12-2.

[0149] The positive electrode material prepared in this embodiment is of type O3, with the general formula being:

[0150] Na 1.01 Cu 0.05 Mn 0.37 Ni 0.2 Fe 0.33 K 0.05 O2.

[0151] Comparative Example 1

[0152] The preparation method of the positive electrode material in this comparative example includes the following steps:

[0153] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, ZrO2 and MnO2 as raw materials according to the molar ratio: Na1.0, Cu0.11, Mn0.33, Ni0.22, Fe0.33, Zr0.01;

[0154] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, denoted as A3.

[0155] The cathode material prepared in this comparative example is of type O3, with the general formula:

[0156] Na 1.0 Cu 0.11 Mn 0.33 Ni 0.22 Fe 0.33 Zr 0.01 O2.

[0157] Comparative Example 2

[0158] The preparation method of the positive electrode material in this comparative example includes the following steps:

[0159] (1) Weigh out Na2CO3, CuO, Fe2O3, Ni(OH)2, ZrO2 and MnO2 as raw materials according to the molar ratio: Na1.2, Cu0.11, Mn0.33, Ni0.22, Fe0.33, Zr0.01;

[0160] (2) Mix the prepared raw materials evenly, dry them, and calcine them at high temperature for 18 hours in a compressed air atmosphere at 980℃ with a heating rate of 3℃ / min. Then crush and sieve them to obtain the positive electrode material, which is denoted as A5.

[0161] The cathode material prepared in this comparative example is of type O3, with the general formula:

[0162] Na 1.2 Cu 0.11 Mn 0.33 Ni 0.22 Fe 0.33 Zr 0.01 O2.

[0163] Comparative Example 3

[0164] One of the cathode materials in this comparative example is of type O3. The general formula and preparation method are the same as those in Example 4, except that the high-temperature calcination temperature is 870°C, and the cathode material is obtained and denoted as C3.

[0165] Comparative Example 4

[0166] One of the cathode materials in this comparative example is of type O3. The general formula and preparation method are the same as those in Example 4, except that the high-temperature calcination temperature is 1060℃, and the cathode material is obtained as C4.

[0167] Experimental Example 1

[0168] Battery assembly: The positive electrode materials of Examples 1-6 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.

[0169] (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.

[0170] Table 1

[0171]

[0172] As can be seen from Table 1, the 0.1C, 0.5C, and 1C capacities of A3, A5, C3, and C4 show significant differences and are relatively low; while the 0.1C, 0.5C, and 1C capacities of B3, B3-1 to B3-10, B12, B12-1, and B12-2 are basically at a similar level and the consistency of the three batteries is good.

[0173] Compared to A3, A5, and B3, the 0.1C capacity is significantly improved. A3 is sodium-poor, A5 is sodium-excessive, and B3 is sodium-rich. B3 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.

[0174] 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.

[0175] (2) The total residual alkali of Examples 1-6 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.

[0176] Residual alkali content test: obtained by Metrohm 888 / 905 instrument.

[0177] Table 2

[0178] Material Mass ratio (sodium carbonate + sodium hydroxide) / % Mass ratio (sodium carbonate) / % Mass ratio (sodium hydroxide) / % B3 2.015 1.980 0.035 B3-1 2.014 1.983 0.031 B3-2 2.012 1.982 0.030 B3-3 2.011 1.980 0.031 B3-4 2.016 1.981 0.035 B3-5 2.018 1.987 0.031 B3-6 2.021 1.984 0.037 B3-7 2.023 1.983 0.040 B3-8 2.024 1.987 0.037 B3-9 2.021 1.985 0.036 B3-10 2.019 1.983 0.036 B10 2.007 1.970 0.037 B11 1.993 1.960 0.033 B12 2.001 1.970 0.031 B12-1 2.036 2.010 0.026 B12-2 2.015 1.980 0.035 A3 1.962 1.930 0.032 A5 2.635 2.550 0.085 C3 2.772 2.342 0.430 C4 2.123 1.968 0.155

[0179] As can be seen from Tables 1 and 2, compared with B3, A3 has a lower total alkali content but its capacity is difficult to achieve. A5 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.

[0180] In addition, compared with C5 and C6, B5, B5-1, and B5-2 only change the sintering temperature. When the temperature is below 880°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.

[0181] (3) The SEM images of materials B3 and B10 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.

[0182] 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 method for preparing a layered oxide cathode material rich in sodium and with low residual alkali content, characterized in that, Includes the following steps: (1) Weigh out each metal source as raw material according to the molar ratio: 1<Na≤1.1, 0.05≤Cu≤0.1, 0.37≤Mn≤0.40, 0.21≤Ni≤0.24, 0.33≤Fe≤0.40, 0<M≤0.05; (2) Mix the prepared raw materials, dry them, calcine them at high temperature, crush them, and sieve them to obtain the positive electrode material; Wherein, 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 high-temperature calcination temperature is (800+400t3)~1050℃, and the calcination time is 8-24h, where t3 is the molar ratio of Ni element; 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 method for preparing the sodium-rich, low-residue layered oxide cathode material according to claim 1, characterized in that, In step (2), the heating rate during high-temperature calcination is 1-5℃ / min.

3. The method for preparing the sodium-rich, low-residue layered oxide cathode material according to claim 1, characterized in that, In step (2), the high-temperature calcination atmosphere is air or oxygen.

4. The method for preparing the sodium-rich, low-residue layered oxide cathode material according to any one of claims 1-3, characterized in that, The general formula of the positive electrode material is Na x3 Cu y3 Mn z3 Ni t3 Fe u3 M a3 O 2+nδ ; where 1 < x3 ≤ 1.1, 0.05 ≤ y3 ≤ 0.1, 0.37 ≤ z3 ≤ 0.40, 0.21 ≤ t3 ≤ 0.24, 0.33 ≤ u3 ≤ 0.40, 0 < a3 ≤ 0.05, 0.34(y3 + z3 + t3 + u3) < u3 / x3 < 0.51(y3 + z3 + t3 + u3) and 0.18(y3 + z3 + t3 + u3) < t3 / x3 < 0.25(y3 + z3 + t3 + u3), x3 + 2y3 + 3z3 + 3u3 + 2a3 + 3t3 < 4 < x3 + 2y3 + 4z3 + 3u3 + 4a3 + 3t3, y3 + z3 + a3 + t3 + u3 = 1, 0 < n ≤ 0.05, -1 ≤ δ ≤ 3.

5. The method for preparing the sodium-rich, low-residue layered oxide cathode material according to any one of claims 1-3, characterized in that, The general formula of the cathode material is Na. x3 Cu y3 Mn z3 Ni t3 Fe u3 (M) a31 M a32 )O 2+nδ M a31 and M a32 In the equation, M represents different elements, where 1 < x³ ≤ 1.1, 0.05 ≤ y³ ≤ 0.1, 0.37 ≤ z³ ≤ 0.40, 0.21 ≤ t³ ≤ 0.24, 0.33 ≤ u³ ≤ 0.40, 0 < a³¹ + a³² ≤ 0.05, 0.34(y³ + z³ + t³ + u³) < u³ / x³ < 0.51(y³ + z³ + t³ + u³) and 0.18(y³ + z³ + t³ + u³) < t³ / x³ < 0.25(y³ + z³ + t³ + u³), x³ + 2y³ + 3z³ + ... 3u3+2(a31+a32)+3t3<4<x3+2y3+4z3+3u3+4(a31+a32)+3t3,y3+z3+(a31+a32)+t3+u3=1,0<n≤0.05,-1≤δ≤3.

6. The method for preparing the sodium-rich, low-residue layered oxide cathode material according to any one of claims 1-3, characterized in that, The general formula of the cathode material is Na. x3 Cu y3 Mn z3 Ni t3 Fe u3 (M) a41 M a42 M a43 )O 2+nδ M a41 M a42 and M a43 In the equation, M represents different elements, where 1 < x³ ≤ 1.1, 0.05 ≤ y³ ≤ 0.1, 0.37 ≤ z³ ≤ 0.40, 0.21 ≤ t³ ≤ 0.24, 0.33 ≤ u³ ≤ 0.40, 0 < a₄¹ + a₄² + a₄³ ≤ 0.05, 0.34(y³ + z³ + t³ + u³) < u³ / x³ < 0.51(y³ + z³ + t³ + u³) and 0.18(y³ + z³ + t³ + u³) < t³ / x³ < 0.25(y³ + z³ + t³ + u³), x³ + 2y³ + 3z³ + ... 3u3+2(a41+a42+a43)+3t3<4<x3+2y3+4z3+3u3+4(a41+a42+a43)+3t3,y3+z3+(a41+a42+a43)+t3+u3=1,0<n≤0.05,-1≤δ≤3.

7. The method for preparing the sodium-rich, low-residue layered oxide cathode material according to any one of claims 1-3, characterized in that, The cathode material is of type O3.

8. The method for preparing the sodium-rich, low-residue layered oxide cathode material according to any one of claims 1-3, characterized in that, The total residual alkali content of the cathode material is 1.6-2.1%.

9. The method for preparing the sodium-rich, low-residue layered oxide cathode material according to claim 8, characterized in that, The sodium carbonate content is 1.2-2.1%, and the sodium hydroxide content is 0.019-0.45%.

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