Iron-based sodium battery positive electrode material, and preparation method therefor and use thereof

Abstract

Provided are an iron-based sodium battery positive electrode material, and a preparation method therefor and the use thereof. The chemical general formula of the iron-based sodium battery positive electrode material is NaxNiaFebMncMdOe, wherein 0.5≤x≤1.5, 0.15≤a≤0.6, 0.05≤b≤0.5, 0.15≤c≤0.78, 0＜d≤0.4, 1.8≤e≤2.2, and M is derived from laterite-nickel ore and comprises any one or a combination of at least two of Li, B, F, P, Si, Mg, Al, Ca, Ti, V, Cu, Zn, Co, Cr, Rb, Sr, Y, Zr, Nb, Mo, Cd or La. By means of element doping, the structural stability of the iron-based sodium battery positive electrode material can be improved, and the increase of the material capacity is promoted, such that the iron-based sodium battery positive electrode material has a relatively high capacity and good cycling performance; in addition, large-scale mass production can also be achieved.

Description

An iron-based sodium cathode material and its preparation method and application Technical Field

[0001] The present application belongs to the field of battery technology and relates to an iron-based sodium cathode material and a preparation method and application thereof. Background Art

[0002] Traditional lithium-ion batteries have some problems, such as limited lithium resources, short battery life, slow charging speed and insufficient capacity. Although modern lithium-ion batteries have achieved a great degree of performance improvement, they still have problems such as overheating, external damage and electrolyte degradation. In comparison, sodium batteries not only have lower costs, longer lifespan, higher energy density and faster charging speed, but also sodium is an element that is more abundant and more widely distributed on the earth, and its mining and transportation have relatively less impact on the environment. Therefore, sodium batteries have lower raw material costs and lower production costs. In addition, sodium batteries do not produce pollutants, which can effectively reduce pressure and damage to the environment and serve as an environmentally friendly energy source.

[0003] Sodium-based cathode materials play a decisive role in the performance of sodium-ion batteries. Currently, layered transition metal oxides are commonly used cathode materials for sodium-ion batteries, with high theoretical specific capacity and excellent electrochemical performance. Among them, iron has a high redox potential, and iron-based sodium-based cathode materials have attracted much attention. However, the current iron-based sodium-based cathode materials have low structural stability and cannot be mass-produced. The capacity and cycle performance need to be further improved.

[0004] Based on the above research, it is necessary to provide an iron-based sodium battery cathode material, which has high structural stability and safety, can be mass-produced, and can improve the capacity and cycle performance of sodium-ion batteries.

[0005] Summary of the Invention

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] The purpose of the present application is to provide an iron-based sodium cathode material and its preparation method and application. The iron-based sodium cathode material can not only improve the structural stability of the material and promote the use of the material capacity through element doping, but also enable the iron-based sodium cathode material to have a higher capacity and excellent cycle performance, and can also be mass-produced.

[0008] To achieve the purpose of this application, this application adopts the following technical solutions:

[0009] In the first aspect, the present invention provides an iron-based sodium cathode material, the chemical formula of which is Na x Nia Fe b Mn c M d O e , wherein 0.5≤x≤1.5, 0.15≤a≤0.6, 0.05≤b≤0.5, 0.15≤c≤0.78, 0<d≤0.4, 1.8≤e≤2.2, M is derived from laterite nickel ore and includes any one or a combination of at least two of Li, B, F, P, Si, Mg, Al, Ca, Ti, V, Cu, Zn, Co, Cr, Rb, Sr, Y, Zr, Nb, Mo, Cd or La.

[0010] In the iron-based sodium cathode material of the embodiment of the present application, the structural stability of the iron-based sodium cathode material is improved by doping with the M element and the combination of Ni, Fe and Mn, which promotes the capacity of the iron-based sodium cathode material, thereby improving the capacity and cycle performance of the iron-based sodium cathode material, and also enables the mass production of the sodium cathode material, solving the problem that the current iron-based sodium cathode material has low structural stability and poor electrochemical performance, thus being unable to be mass-produced and applied on a large scale.

[0011] The 0.5≤x≤1.5 may be, for example, 0.5, 1.0 or 1.5, 0.15≤a≤0.6 may be, for example, 0.15, 0.3 or 0.6, 0.05≤b≤0.5 may be, for example, 0.05, 0.25 or 0.5, 0.15≤c≤0.78 may be, for example, 0<d≤0.4, 0.1, 0.2, 0.3 or 0.4, 1.8≤e≤2.2 may be, for example, 1.8, 2.0 or 2.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0012] In the embodiment of the present application, M is an element that replaces the transition metal site (Ni, Fe and Mn) by doping. The doping elements represented by M are all derived from laterite nickel ore. x, a, b, c and d are the molar percentages of the corresponding elements, respectively. The components in the general chemical formula satisfy the conservation of charge and the conservation of stoichiometry.

[0013] The M includes any one or a combination of at least two of Li, B, F, P, Si, Mg, Al, Ca, Ti, V, Cu, Zn, Co, Cr, Rb, Sr, Y, Zr, Nb, Mo, Cd or La, preferably M is any one of Cu, Zn, Mg, Ti, Zr or Nb, more preferably a combination of at least two of Cu, Zn, Mg, Ti, Zr or Nb.

[0014] When the doping elements in the embodiment of the present application are preferably a combination of at least two of Cu, Zn, Mg, Ti, Zr or Nb, the synergistic effect between the different elements can be exerted, thereby obtaining an iron-based sodium cathode material with excellent comprehensive performance.

[0015] When the M is selected from a combination of any two of Cu, Zn, Mg, Ti, Zr or Nb, the molar ratio of the any two elements is (1-3): (1-3), for example, it can be 1:1, 1:3 or 3:1; when the M is selected from a combination of any three of Cu, Zn, Mg, Ti, Zr or Nb, the molar ratio of the any two elements is (1-3): (1-3): (1-3), for example, it can be 1:1:1, 1:3:3 or 3:1:3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] In one embodiment, when M is any one of Cu, Zn, Mg or Ti or a combination of at least two thereof, d is 0.03-0.4, for example, 0.03, 0.2, 0.3 or 0.4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In one embodiment, when M is Zr and / or Nb, d is 5×10 -5 ~0.05, for example, it can be 5×10 -5 , 5×10 -4 , 5×10 -3 or 0.05, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Due to the differences between elements, the embodiments of the present application correspond to different doping amounts when selecting different doping elements, which can not only provide guidance for the selection of doping elements and doping amounts, but also play the optimal role of the doping elements and make the doping elements and doping amounts cooperate with each other.

[0019] In a second aspect, an embodiment of the present application provides a method for preparing the iron-based sodium cathode material as described in the first aspect, the preparation method comprising the following steps:

[0020] (1) feeding nickel iron manganese salt solution, M salt solution, complexing agent solution and precipitant solution to carry out coprecipitation reaction to obtain a precursor;

[0021] (2) Mixing and sintering the sodium source with the precursor in step (1) to obtain the iron-based sodium cathode material.

[0022] The iron-based sodium cathode material of the embodiment of the present application is prepared by a co-precipitation reaction to obtain a precursor, and then sintered with a sodium source to obtain the final product. The preparation method is simple and does not require an additional doping step. It only requires adding a doping salt solution during co-precipitation.

[0023] In one embodiment, the feeding method of the nickel-iron-manganese salt solution and the M salt solution in step (1) includes: mixing the nickel-iron-manganese salt solution and the M salt solution into a mixed liquid and feeding them together, or feeding them separately without mixing. Preferably, the nickel-iron-manganese salt solution and the M salt solution are mixed into a mixed liquid and fed together.

[0024] In one embodiment, after the mixed liquid is mixed, the flow rate of the feed together is 1-200 L / h, for example, it can be 1 L / h, 50 L / h, 100 L / h, 150 L / h or 200 L / h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In one embodiment, the flow rate of the co-feed is gradually increased in the range of 1-200 L / h, wherein the flow increase rate is 20-60 L / h, for example, it can be 20 L / h, 30 L / h, 40 L / h, 50 L / h or 60 L / h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In the embodiment of the present application, the nickel-iron-manganese salt solution and the M salt solution are preferably mixed and fed together, which not only saves steps but also improves the uniformity of distribution between elements. At the same time, when the mixed solution described in the embodiment of the present application is fed, the flow rate increases from small to large, which can greatly improve the yield, save time, and is also beneficial to improving the electrochemical properties of the iron-based sodium cathode material. However, the flow increase rate should not be too large, as it will affect the product morphology and thus deteriorate the material properties.

[0027] In one embodiment, when the M salt solution in step (1) includes Mg, Ca, Ti, Cu, Zn or Co elements, the nickel-iron-manganese salt solution and the M salt solution are mixed into a mixed solution and fed together.

[0028] In one embodiment, when the M salt solution in step (1) includes Li, B, F, P, Si, Al, V, Cr, Rb, Sr, Y, Zr, Nb, Mo, Cd or La elements, the nickel-iron-manganese salt solution and the M salt solution are not mixed and fed separately.

[0029] Among the elements doped in the embodiments of the present application, due to the differences between the elements, some elements can be mixed with the nickel-iron-manganese salt solution and fed simultaneously, while some elements can only be fed separately from the nickel-iron-manganese salt solution. Therefore, different doping elements in the embodiments of the present application adaptably select different feeding methods, which further provides guidance for element doping.

[0030] In one embodiment, the feed flow rate of the precipitant solution in step (1) is 0.2-80 L / h, for example, 0.2 L / h, 20 L / h, 50 L / h or 80 L / h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In one embodiment, the feed flow rate of the complexing agent solution in step (1) is 0.05-30 L / h, for example, 0.05 L / h, 10 L / h, 20 L / h or 30 L / h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] In one embodiment, the mass concentration of the nickel-iron-manganese salt solution in step (1) is 80-120 g / L, for example, 80 g / L, 100 g / L or 120 g / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 100 g / L.

[0033] In one embodiment, in the nickel-iron-manganese salt solution of step (1), the molar ratio of nickel ions, iron ions and manganese ions is 3:3:3, 2:4:2 or 2:2:4.

[0034] In the iron-based sodium cathode material of the embodiment of the present application, the electrical performance is optimal when the molar ratio of nickel element, iron element and manganese element is 3:3:3, 2:4:2 or 2:2:4.

[0035] In one embodiment, the concentration of M ions in the M salt solution of step (1) is 0.001-3 mol / L, for example, 0.001 mol / L, 1 mol / L, 2 mol / L or 3 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] In one embodiment, the concentration of the precipitant solution in step (1) is 8-11 mol / L, for example, 8 mol / L, 9 mol / L, 10 mol / L or 11 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] In one embodiment, the concentration of the complexing agent solution in step (1) is 0.1-11 mol / L, for example, 0.1 mol / L, 5 mol / L or 11 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] In one embodiment, the pH of the coprecipitation reaction in step (1) is 6.5-13, for example, 6.5, 10 or 13, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 8.5-12.

[0039] In one embodiment, the temperature of the coprecipitation reaction in step (1) is 30-80°C, for example, 30°C, 50°C, 70°C or 80°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 35-75°C.

[0040] In one embodiment, the coprecipitation reaction in step (1) is carried out under stirring, and the stirring rate is 180-1200 rpm, for example, it can be 180 rpm, 500 rpm or 1200 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In one embodiment, the particle size D50 of the reaction product of the coprecipitation reaction in step (1) is 3-15 μm, for example, 3 μm, 5 μm, 10 μm or 15 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In one embodiment, after the coprecipitation reaction in step (1), aging, washing and drying steps are sequentially performed to obtain a precursor.

[0043] In one embodiment, the salt used in the nickel-iron-manganese salt solution in step (1) includes any one of sulfate, nitrate, chloride or acetate, or a combination of at least two of them.

[0044] In one embodiment, the precipitant solution in step (1) comprises any one of sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate, or a combination of at least two thereof.

[0045] In one embodiment, the complexing agent solution in step (1) comprises any one of ammonia water, acetic acid, citric acid, EDTA (ethylenediaminetetraacetic acid), salicylic acid or acetylacetone, or a combination of at least two thereof.

[0046] In one embodiment, the molar ratio of sodium ions in the sodium source in step (2) to metal ions in the precursor is (0.75-1.2):1, for example, it can be 0.75:1, 1:1 or 1.2:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In one embodiment, the sintering temperature in step (2) is 600-1000°C, for example, it can be 600°C, 800°C or 1000°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 700-900°C; the sintering time is 8-20h, for example, it can be 8h, 15h or 20h, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 10-15h.

[0048] As a preferred technical solution of the preparation method described in the examples of this application, the preparation method comprises the following steps:

[0049] (1) mixing a nickel iron manganese salt solution and an M salt solution into a mixed solution, feeding the mixed solution with a complexing agent solution and a precipitant solution, and performing a coprecipitation reaction at a temperature of 30-80° C., a pH of 8.5-12, and a stirring rate of 180-1200 rpm until the particle size D50 of the reaction product is 3-15 μm, thereby obtaining a precursor;

[0050] The flow rate of the mixed solution feed is gradually increased in the range of 1-200 L / h, wherein the flow rate is 20-60 L / h; the mass concentration of the nickel-iron-manganese salt solution is 80-120 g / L; the concentration of M ions in the M salt solution is 0.001-3 mol / L; the feed flow rate of the precipitant solution is 0.2-80 L / h, and the concentration is 8-11 mol / L; the feed flow rate of the complexing agent solution is 0.05-30 L / h, and the concentration is 0.1-11 mol / L;

[0051] (2) mixing a sodium source with the precursor of step (1), wherein the molar ratio of sodium ions in the sodium source to metal ions in the precursor is (0.75-1.2):1, and then sintering at 600-1000°C for 8-20h to obtain the iron-based sodium cathode material.

[0052] In a third aspect, an embodiment of the present application provides a sodium ion battery, which includes the iron-based sodium cathode material as described in the first aspect.

[0053] Compared with the prior art, this application has the following beneficial effects:

[0054] The present application improves the structural stability of the iron-based sodium cathode material by doping with the M element, promotes the capacity of the iron-based sodium cathode material, thereby improving the capacity and cycle performance of the iron-based sodium cathode material, and can also enable the mass production of the sodium cathode material, solving the problem that the current iron-based sodium cathode material has low structural stability and poor electrochemical performance, which makes it impossible to mass produce and apply on a large scale. DETAILED DESCRIPTION

[0055] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0056] Example 1

[0057] This embodiment provides an iron-based sodium cathode material. The chemical formula of the iron-based sodium cathode material is Na 0.94 Ni 0.33 Fe 0.34 Mn 0.33 Cu 0.05 O 2.03 ;

[0058] The preparation method of the iron-based sodium cathode material comprises the following steps:

[0059] (1) mixing a nickel-iron-manganese salt solution and an M salt solution to form a mixed solution, and then feeding the mixed solution, a sodium hydroxide solution, and an ammonia solution in parallel, and performing a coprecipitation reaction at a temperature of 50° C., a pH of 11, and a stirring rate of 500 rpm until the particle size D50 of the reaction product is 8 μm, and then separating the solid phase, aging the solid phase, washing, and drying the solid phase to obtain a precursor;

[0060] The flow rate of the mixed solution feed is gradually increased within the range of 10-200 L / h, wherein the flow rate is 40 L / h; the mass concentration of the nickel-iron-manganese salt solution is 100 g / L, and the molar ratio of nickel ions, iron ions, and manganese ions is 1:1:1; in the M salt solution, the concentration of M ions is 0.1 mol / L, and the M ions are copper ions; the feed flow rate of the sodium hydroxide solution is 5 L / h, and the concentration is 11 mol / L; the feed flow rate of the ammonia water is 1 L / h, and the concentration is 9 mol / L;

[0061] (2) mixing sodium carbonate with the precursor of step (1) in a planetary mixer, wherein the molar ratio of sodium ions in the sodium source to metal ions in the precursor is 1:1, and then sintering at a temperature of 700°C in a resistance furnace at a heating rate of 5°C / min for 18 hours to obtain the iron-based sodium cathode material.

[0062] Example 2

[0063] This embodiment provides an iron-based sodium cathode material. The chemical formula of the iron-based sodium cathode material is Na 0.94 Ni 0.30 Fe 0.15 Mn 0.55 Cu 0.05 O 2.03 ;

[0064] The preparation method of the iron-based sodium cathode material comprises the following steps:

[0065] (1) mixing a nickel-iron-manganese salt solution and an M salt solution into a mixed solution, and then feeding the mixed solution, a sodium hydroxide solution, and an ammonia solution in parallel, and performing a coprecipitation reaction at a temperature of 30° C., a pH of 8.5, and a stirring rate of 180 rpm until the particle size D50 of the reaction product is 15 μm, and then separating the solid phase, aging the solid phase, washing, and drying the solid phase to obtain a precursor;

[0066] The flow rate of the mixed solution feed is gradually increased within the range of 1-200 L / h, wherein the flow rate is 60 L / h; the mass concentration of the nickel-iron-manganese salt solution is 80 g / L, and the molar ratio of nickel ions, iron ions, and manganese ions is 3:1.5:5.5; in the M salt solution, the concentration of M ions is 0.1 mol / L, and the M ions are copper ions; the feed flow rate of the sodium hydroxide solution is 1 L / h, and the concentration is 11 mol / L; the feed flow rate of the ammonia solution is 1 L / h, and the concentration is 11 mol / L;

[0067] (2) mixing sodium carbonate with the precursor of step (1) in a planetary mixer, wherein the molar ratio of sodium ions in the sodium source to metal ions in the precursor is 1:1, and then sintering at a temperature of 600°C in a resistance furnace at a heating rate of 5°C / min for 20 hours to obtain the iron-based sodium cathode material.

[0068] Example 3

[0069] This embodiment provides an iron-based sodium cathode material. The chemical formula of the iron-based sodium cathode material is Na 1.04 Ni 0.33 Fe 0.34 Mn 0.33 Cu 0.005 O 2.1 ;

[0070] The preparation method of the iron-based sodium cathode material comprises the following steps:

[0071] (1) mixing a nickel-iron-manganese salt solution and an M salt solution into a mixed solution, and then feeding the mixed solution, a sodium hydroxide solution, and an ammonia solution in parallel, and performing a coprecipitation reaction at a temperature of 30° C., a pH of 12, and a stirring rate of 1200 rpm until the particle size D50 of the reaction product is 3 μm, and then separating the solid phase, aging the solid phase, washing, and drying the solid phase to obtain a precursor;

[0072] The flow rate of the mixed liquid feed is gradually increased in the range of 1-200 L / h, wherein the flow rate is 20 L / h; the mass concentration of the nickel-iron-manganese salt solution is 120 g / L, and the molar ratio of nickel ions, iron ions and manganese ions is 1:1:1; in the M salt solution, the concentration of M ions is 0.01 mol / L, and the M ions are copper ions; the feed flow rate of the sodium hydroxide solution is 80 L / h, and the concentration is 8 mol / L; the feed flow rate of the ammonia water is 30 L / h, and the concentration is 0.1 mol / L;

[0073] (2) mixing sodium carbonate with the precursor of step (1) in a planetary mixer, wherein the molar ratio of sodium ions in the sodium source to metal ions in the precursor is 1.2:1, and then sintering at a temperature of 1000° C. for 8 h in a resistance furnace at a heating rate of 5° C. / min to obtain the iron-based sodium cathode material.

[0074] Example 4

[0075] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in its preparation process, the M ion in step (1) is a zinc ion, which changes the adaptability of the iron-based sodium cathode material.

[0076] Example 5

[0077] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in its preparation process, the M ions in step (1) are magnesium ions, which changes the adaptability of the iron-based sodium cathode material.

[0078] Example 6

[0079] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in its preparation process, the M ions in step (1) are titanium ions, which changes the adaptability of the iron-based sodium cathode material.

[0080] Example 7

[0081] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in the preparation process, the M ions in step (1) are zirconium ions, which changes the adaptability of the iron-based sodium cathode material.

[0082] Example 8

[0083] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in its preparation process, the M ions in step (1) are niobium ions, which changes the adaptability of the iron-based sodium cathode material.

[0084] Example 9

[0085] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in its preparation process, the M ions in step (1) are copper ions and zinc ions with a molar ratio of 1:1, which changes the adaptability of the iron-based sodium cathode material.

[0086] Example 10

[0087] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in its preparation process, the M ions in step (1) are copper ions, zinc ions and titanium ions with a molar ratio of 1:1:1, so that the adaptability of the iron-based sodium cathode material changes.

[0088] Example 11

[0089] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in the preparation process, the molar ratio of nickel ions, iron ions and manganese ions in the nickel-iron-manganese salt solution in step (1) is 1:1:4.

[0090] Example 12

[0091] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that in Example 1 except that in the preparation process, the mixed solution in step (1) is fed at a fixed flow rate of 15 L / h to adapt the iron-based sodium cathode material.

[0092] Example 13

[0093] This embodiment provides an iron-based sodium cathode material. The preparation process of the iron-based sodium cathode material is the same as that of Example 1, except that the flow rate of the mixed solution in step (1) is 70 L / h to adapt the iron-based sodium cathode material.

[0094] Example 14

[0095] This embodiment provides an iron-based sodium cathode material. The preparation process of the iron-based sodium cathode material is the same as that of Example 1, except that the flow rate of the mixed solution in step (1) is 0.5 L / h to adapt the iron-based sodium cathode material.

[0096] Comparative Example 1

[0097] This embodiment provides an iron-based sodium cathode material. The iron-based sodium cathode material is the same as that of Example 1 except that no M salt solution is added in step (1) during its preparation.

[0098] The iron-based sodium cathode materials obtained in the above embodiments and comparative examples were prepared into cathode sheets, which were then assembled into batteries with sodium anode sheets to test their electrochemical properties. The rate performance test was conducted on a voltage platform of 3.2-4.1 V, with different cathode materials subjected to 300 charge and discharge tests at a current density of 1.0 C, and the discharge specific capacity of different samples at a current density of 1.0 C was recorded. The cycle performance test method was to measure the capacity retention rate of different samples after 300 cycles at 1.0 C. The test results were based on the results of Example 1 as 100%, and the test results of other samples were expressed as relative percentages relative to Example 1.

[0099] The test results are shown in Table 1 below:

[0100] Table 1

[0101] From the above table we can see that:

[0102] The iron-based sodium cathode material obtained in the present application has excellent electrochemical properties, and it can be seen from Example 1 and Comparative Example 1 that element doping can effectively improve the material capacity and cycle performance; it can be seen from Example 1 and Examples 9-10 that when multiple elements are used for doping in the present application, the synergistic effect between the multiple elements can be exerted, thereby further improving the performance of the material; it can be seen from Example 1 and Example 11 that in the material of the present application, when the molar ratio of nickel, iron and manganese elements adopts a preferred ratio, the material performance can be further improved; it can be seen from Example 1 and Examples 12-14 that when the mixed liquid of the present application is fed, the feed rate is preferably gradually increased, and when the flow rate increase rate is within a reasonable range, the material performance can be further improved.

[0103] In summary, the present application provides an iron-based sodium cathode material and its preparation method and application. The iron-based sodium cathode material can not only improve the structural stability of the material and promote the use of the material capacity through element doping, so that the iron-based sodium cathode material has a higher capacity and excellent cycle performance, but also can be mass-produced.

[0104] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. An iron-based sodium positive electrode material, the chemical formula of the iron-based sodium positive electrode material is Na x Ni a Fe b Mn c M d O e ,in, 0.5≤x≤1.5, 0.15≤a≤0.6, 0.05≤b≤0.5, 0.15≤c≤0.78, 0<d≤0.4, 1.8≤e≤2.2, M is derived from laterite nickel ore, including any one or a combination of at least two of Li, B, F, P, Si, Mg, Al, Ca, Ti, V, Cu, Zn, Co, Cr, Rb, Sr, Y, Zr, Nb, Mo, Cd or La.

2. The iron-based sodium positive electrode material according to claim 1, wherein: The M is any one of Cu, Zn, Mg, Ti, Zr or Nb.

3. The iron-based sodium positive electrode material according to claim 1 or 2, wherein: The M is a combination of at least two of Cu, Zn, Mg, Ti, Zr or Nb.

4. The iron-based sodium positive electrode material according to any one of claims 1 to 3, wherein: When M is any one of Cu, Zn, Mg or Ti or a combination of at least two of them, d is 0.03-0.

4.

5. The iron-based sodium positive electrode material according to any one of claims 1 to 4, wherein: When M is Zr and / or Nb, d is 5×10 -5 ~0.

05.

6. A method for preparing the iron-based sodium cathode material according to any one of claims 1 to 5, the method comprising the following steps: (1) feeding a nickel-iron-manganese salt solution, an M salt solution, a complexing agent solution and a precipitant solution to perform a coprecipitation reaction to obtain a precursor; (2) Mixing and sintering the sodium source with the precursor in step (1) to obtain the iron-based sodium positive electrode material.

7. The preparation method according to claim 6, wherein: The method for feeding the nickel-iron-manganese salt solution and the M salt solution in step (1) comprises: mixing the nickel-iron-manganese salt solution and the M salt solution into a mixed solution and feeding them together, or feeding them separately without mixing; Optionally, after the mixture is mixed into a mixed liquid, the flow rate of the feed together is 1-200 L / h; Optionally, the flow rate of the co-feed is gradually increased within the range of 1-200 L / h, wherein the flow increase rate is 20-60 L / h; Optionally, when the M salt solution in step (1) includes Mg, Ca, Ti, Cu, Zn or Co elements, the nickel-iron-manganese salt solution and the M salt solution are mixed into a mixed solution and fed together; Optionally, when the M salt solution in step (1) includes Li, B, F, P, Si, Al, V, Cr, Rb, Sr, Y, Zr, Nb, Mo, Cd or La elements, the nickel-iron-manganese salt solution and the M salt solution are not mixed but fed separately.

8. The preparation method according to claim 6 or 7, wherein: The feed flow rate of the precipitant solution in step (1) is 0.2-80 L / h; Optionally, the feed flow rate of the complexing agent solution in step (1) is 0.05-30 L / h.

9. The preparation method according to any one of claims 6 to 8, wherein: The mass concentration of the nickel-iron-manganese salt solution in step (1) is 80-120 g / L; Optionally, in the M salt solution of step (1), the concentration of M ions is 0.001-3 mol / L; Optionally, the concentration of the precipitant solution in step (1) is 8-11 mol / L; Optionally, the concentration of the complexing agent solution in step (1) is 0.1-11 mol / L.

10. The preparation method according to any one of claims 6 to 9, wherein: The pH of the coprecipitation reaction in step (1) is 6.5-13; Optionally, the pH of the coprecipitation reaction in step (1) is 8.5-12; Optionally, the temperature of the coprecipitation reaction in step (1) is 30-80° C.; Optionally, the coprecipitation reaction in step (1) is carried out under stirring at a rate of 180-1200 rpm; Optionally, the coprecipitation reaction in step (1) is performed until the particle size D50 of the reaction product is 3-15 μm; Optionally, after the coprecipitation reaction in step (1), aging, washing and drying steps are sequentially performed. Get the precursor.

11. The preparation method according to any one of claims 6 to 10, wherein: The salt used in the nickel-iron-manganese salt solution in step (1) includes any one of sulfate, nitrate, chloride or acetate, or a combination of at least two thereof; Optionally, the precipitant solution in step (1) comprises any one of sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate, or a combination of at least two thereof; Optionally, the complexing agent solution in step (1) includes any one of ammonia water, acetic acid, citric acid, EDTA, salicylic acid or acetylacetone, or a combination of at least two thereof; Optionally, the molar ratio of sodium ions in the sodium source in step (2) to metal ions in the precursor is (0.75-1.2):1; Optionally, the sintering temperature in step (2) is 600-1000° C. and the sintering time is 8-20 h.

12. The preparation method according to any one of claims 6 to 11, wherein: The preparation method comprises the following steps: (1) mixing a nickel iron manganese salt solution and an M salt solution into a mixed solution, feeding the mixed solution with a complexing agent solution and a precipitant solution, and performing a coprecipitation reaction at a temperature of 30-80° C., a pH of 8.5-12, and a stirring rate of 180-1200 rpm until the particle size D50 of the reaction product is 3-15 μm, thereby obtaining a precursor; The flow rate of the mixed solution feed is gradually increased in the range of 1-200 L / h, wherein the flow rate is 20-60 L / h; the mass concentration of the nickel-iron-manganese salt solution is 80-120 g / L; in the M salt solution, the concentration of M ions is 0.001-3 mol / L; the feed flow rate of the precipitant solution is 0.2-80 L / h, and the concentration is 8-11 mol / L; the feed flow rate of the complexing agent solution is 0.05-30 L / h, and the concentration is 0.1-11 mol / L; (2) Mixing a sodium source with the precursor of step (1), wherein the molar ratio of sodium ions in the sodium source to metal ions in the precursor is (0.75-1.2):1, and then sintering at 600-1000° C. for 8-20 hours to obtain the iron-based sodium cathode material.

13. A sodium ion battery, comprising the iron-based sodium cathode material according to any one of claims 1 to 5.

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