Sodium-ion battery positive electrode material, preparation method and application thereof, and sodium-ion battery

Abstract

The application relates to the field of sodium ion battery positive electrode materials, discloses a sodium ion battery positive electrode material, a preparation method and application of the sodium ion battery positive electrode material and a sodium ion battery. The positive electrode material contains positive electrode material A and positive electrode material B; the positive electrode material A is a single crystal particle, the positive electrode material B is an agglomerate; the positive electrode material A and the positive electrode material B each independently have a (002) crystal face and / or a (003) crystal face characteristic diffraction peak at 2theta of 14-18 degrees, and the 2theta angle of the (002) crystal face characteristic diffraction peak is smaller than the 2theta angle of the (003) crystal face characteristic diffraction peak; the positive electrode material A at least has the (002) crystal face characteristic diffraction peak, and the positive electrode material B at least has the (003) crystal face characteristic diffraction peak. The positive electrode material is structurally stable at high voltage, and has good cycle performance.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery cathode material technology, specifically to sodium-ion battery cathode materials, their preparation methods, applications, and sodium-ion batteries. Background Technology

[0002] In recent years, sodium-ion batteries have received widespread attention as a complementary technology to lithium-ion batteries. Due to the abundance and low price of sodium resources, and against the backdrop of rapidly rising prices of lithium and cobalt resources, sodium-ion batteries can significantly reduce battery manufacturing costs and are expected to be widely used in low-speed electric vehicles and energy storage.

[0003] In sodium-ion battery systems, one of the most critical materials is the cathode material. Cathode materials include layered oxide cathode materials, Prussian blue cathode materials, and polyanionic cathode materials. Among them, layered oxide NaMeO2 (Me = Ni, Fe, Mn, etc.) cathode materials are widely recognized as the most promising cathode materials for sodium-ion batteries due to their advantages such as simple structure, adjustable element content, ease of large-scale production, and excellent electrochemical performance.

[0004] Layered oxides are mainly classified into two structures, P2 type and O3 type, based on the different sodium occupancy methods and oxygen layer stacking order. Among them, P2 type layered oxides exhibit better rate capability, while O3 type layered oxides exhibit higher theoretical capacity.

[0005] However, both P2-type and O3-type layered oxides exhibit high voltage (>4.2V, vs. Na) characteristics. + The complex phase transition of Na+ leads to structural damage and rapid capacity decay, which greatly limits the further development of layered oxide materials. Summary of the Invention

[0006] The purpose of this invention is to overcome the aforementioned problems of existing layered oxide sodium-ion battery cathode materials, and to provide a sodium-ion battery cathode material, its preparation method, applications, and a sodium-ion battery. This sodium-ion battery cathode material is a multiphase composite oxide cathode material; through the synergistic effect between the composite phases, the cycle performance of the cathode material can be significantly improved.

[0007] To achieve the above objectives, a first aspect of the present invention provides a sodium-ion battery cathode material, wherein the sodium-ion battery cathode material comprises cathode material A and cathode material B; wherein cathode material A is a single crystal particle, and cathode material B is an aggregate; and...

[0008] In the XRD patterns of the cathode material A and the cathode material B, each independently has characteristic diffraction peaks of the (002) crystal plane and / or the (003) crystal plane at a 2θ of 14°-18°, and the 2θ angle of the characteristic diffraction peak of the (002) crystal plane is smaller than the 2θ angle of the characteristic diffraction peak of the (003) crystal plane.

[0009] Wherein, the cathode material A has at least the characteristic diffraction peak of the (002) crystal plane, and the cathode material B has at least the characteristic diffraction peak of the (003) crystal plane.

[0010] A second aspect of the present invention provides a method for preparing the sodium-ion battery cathode material described in the first aspect, the method comprising: mixing cathode material A and cathode material B;

[0011] Preferably, the method for preparing the positive electrode material A includes:

[0012] (1) In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant and a complexing agent are mixed to carry out a first coprecipitation reaction to obtain precursor I;

[0013] (2) The precursor I is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and subjected to a first sintering to obtain the cathode material A;

[0014] Preferably, the method for preparing the positive electrode material B includes:

[0015] (a) In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant and a complexing agent are mixed to carry out a second coprecipitation reaction to obtain precursor II;

[0016] (b) The precursor II is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and then subjected to a second sintering to obtain the cathode material B.

[0017] The third aspect of this invention provides the application of the sodium-ion battery cathode material described in the first aspect, or the preparation method described in the second aspect, in a sodium-ion battery.

[0018] A fourth aspect of the present invention provides a sodium-ion battery, wherein the sodium-ion battery contains the sodium-ion battery positive electrode material described in the first aspect.

[0019] Through the above technical solution, the sodium-ion battery cathode material provided by the present invention is a multiphase composite oxide cathode material with synergistic addition. Cathode material A is a single-crystal particle, exhibiting good rate performance and cycle performance. Furthermore, cathode material A also possesses characteristic diffraction peaks of the (002) crystal plane at 2θ of 14°-18°, thus exhibiting a relatively broad Na+ ionization curve. + Transport channels and abundant sodium vacancies, with a large Na layer spacing, Na+ Direct diffusion between two adjacent triangular prism sites can enhance the Na ion transport rate and maintain the integrity of the layered structure, thus resulting in better rate performance and cycle performance. Cathode material B is an agglomerate, which means it has a high capacity. At the same time, cathode material B also has a characteristic diffraction peak of the (003) crystal plane at 2θ of 14°-18°. Cathode material B has a high Na / Me ratio, thus having a higher capacity. The sodium-ion battery cathode material obtained by mixing cathode material A and cathode material B can minimize the phase transition in the entire wide potential region, thereby alleviating the structural damage of the layered oxide under high voltage. Through the synergistic effect between the composite phases, the cycle performance of the sodium-ion battery cathode material is greatly improved.

[0020] In a preferred embodiment, the particle sizes of cathode material A and cathode material B are respectively limited to form a hierarchical structure in the sodium-ion battery cathode material. By mixing single-crystal cathode material A and agglomerated cathode material B in a weight ratio within a specified range, a higher compaction density can be obtained, which enables the sodium-ion battery cathode material to have higher structural stability and better cycle stability while ensuring high rate and high capacity performance output.

[0021] Furthermore, the preparation method provided by the present invention, on the one hand, controls the D of precursor I and precursor II. 50 By controlling the range of values ​​for n(Na) / n(Me) in cathode materials A and B, cathode materials A and B with narrow particle size distribution ranges are obtained, resulting in more uniform materials for blending and stable electrical performance. On the other hand, by controlling the ratio of n(Na) / n(Me) in cathode materials A and B respectively, cathode material A with at least a (002) crystal plane characteristic diffraction peaks is obtained, giving it a P2 or P2 / O3 type crystal structure, and cathode material B with at least a (003) crystal plane characteristic diffraction peaks is obtained, giving it an O3 or O3 type crystal structure. The P2 / O3 type crystal structure was used. Then, during sintering, the sintering temperature, heating rate, oxygen content, and doping elements of cathode materials A and B were controlled. This resulted in cathode material A forming a small-particle single-crystal structure, further enhancing its Na-ion transport rate; and cathode material B forming large-particle aggregates, enabling it to release more sodium ions, minimizing phase transitions across the entire wide potential range, and mitigating structural damage to the layered oxide under high voltage. Finally, by controlling the weight ratio of cathode materials A and B, a higher compaction density was achieved.

[0022] In summary, the cathode material A obtained by the preparation method provided by this invention exhibits excellent rate performance and cycle performance; the cathode material B obtained is able to release more sodium ions. Mixing cathode material A and cathode material B yields a sodium-ion battery cathode material that, while ensuring high rate and high capacity output, also possesses high compaction density, high structural stability, and good cycle stability. Attached Figure Description

[0023] Figure 1 These are SEM images of precursor I prepared in Example 1 of this invention;

[0024] Figure 2 These are SEM images of precursor II prepared in Example 1 of this invention;

[0025] Figure 3 These are SEM images of the cathode material A prepared in Example 1 of this invention;

[0026] Figure 4 These are SEM images of the cathode material B prepared in Example 1 of this invention;

[0027] Figure 5 These are SEM images of the sodium-ion battery cathode material prepared in Example 1 of this invention;

[0028] Figure 6 This is the XRD pattern of the P2-type single-crystal cathode material A prepared in Example 1 of this invention;

[0029] Figure 7 This is the XRD pattern of the O3-type agglomerated cathode material B prepared in Example 1 of this invention;

[0030] Figure 8 This is the XRD pattern of the P2 / O3 type agglomerated cathode material B prepared in Example 2 of the present invention. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] In this invention, unless otherwise specified, “first,” “second,” “third,” and “fourth” do not represent a sequence or limit the materials or operations, but are merely used to distinguish between them. For example, “first” and “second” in “first insulation stage” and “second insulation stage” are only used to distinguish them and indicate that they are not the same insulation stage.

[0033] Unless otherwise specified, the room temperature referred to in this invention is 25±2℃.

[0034] Unless otherwise stated in this invention, the term "P2-type single crystal material" refers to a single crystal cathode material with a P2-type crystal structure; the term "P2 / O3-type single crystal material" refers to a composite phase single crystal cathode material with a P2 / O3 transition crystal structure; the term "P2 / O3-type agglomerated material" refers to a composite phase agglomerated cathode material with a P2 / O3 transition crystal structure; and the term "O3-type agglomerated material" refers to an agglomerated cathode material with an O3-type crystal structure.

[0035] Unless otherwise stated in this invention, "Me" refers to the collective term for the elements Ni, Fe, Mn, M, and M′; "n(Na) / n(Me)" refers to n(Na) / n(Ni+Fe+Mn+M+M′), ​​which is the ratio of the total molar amount of Na to the total molar amount of Ni+Fe+Mn+M+M′.

[0036] The first aspect of this invention provides a sodium-ion battery cathode material, wherein the sodium-ion battery cathode material comprises cathode material A and cathode material B;

[0037] Wherein, cathode material A is a single crystal particle, and cathode material B is an aggregate; and,

[0038] In the XRD patterns of the cathode material A and the cathode material B, each independently has characteristic diffraction peaks of the (002) crystal plane and / or the (003) crystal plane at a 2θ of 14°-18°, and the 2θ angle of the characteristic diffraction peak of the (002) crystal plane is smaller than the 2θ angle of the characteristic diffraction peak of the (003) crystal plane.

[0039] Wherein, the cathode material A has at least the characteristic diffraction peak of the (002) crystal plane, and the cathode material B has at least the characteristic diffraction peak of the (003) crystal plane.

[0040] During their research, the inventors of this invention discovered that when the XRD test results of cathode material A and cathode material B contained in the cathode material of a sodium-ion battery meet the above conditions, the phase transition in the entire wide potential region can be minimized, thereby alleviating the structural damage of layered oxides under high voltage, producing a synergistic effect on electrochemical performance, and significantly improving the electrochemical performance of the cathode material of a sodium-ion battery.

[0041] According to some embodiments of the present invention, preferably, the median particle size D of the positive electrode material A is... 50 The micrometer size is 1-5 μm, preferably 2-4 μm, and more preferably 3.6-4 μm;

[0042] According to some embodiments of the present invention, preferably, the median particle size D of the positive electrode material B is... 50 The micrometer size is 6-16 μm, preferably 8-14 μm, and more preferably 12.3-13.9 μm.

[0043] The above-described preferred embodiments are beneficial for further improving the rate performance of sodium-ion battery cathode materials, and at the same time, further increasing the capacity of sodium-ion battery cathode materials.

[0044] According to some embodiments of the present invention, preferably, the median particle size D of the sodium-ion battery cathode material is... 50 The size is 1-20 μm, preferably 5-15 μm.

[0045] According to some embodiments of the present invention, preferably, the weight ratio of the positive electrode material A to the positive electrode material B is 1:0.1-9, more preferably 1:0.4-2.5. Adopting the above preferred embodiments is beneficial to promoting the synergistic performance of positive electrode material A and positive electrode material B, thereby maximizing the compatibility of the cycle performance and capacity of the sodium-ion battery positive electrode material.

[0046] This invention improves the compaction density of the sodium-ion battery cathode material and the volumetric energy density of the electrode containing the sodium-ion battery cathode material by hierarchically controlling the particle size distribution of cathode material A and cathode material B contained in the cathode material.

[0047] According to some embodiments of the present invention, preferably, the positive electrode material A has the composition shown in Formula I:

[0048] Na a1 (Ni x1 Fe y1 Mn z1 M m1 M′ n1 O2 formula I;

[0049] In the formula, 0.50≤a1≤1.10, 0≤x1≤0.5, 0≤y1≤0.5, 0≤z1≤0.5, 0≤m1≤0.5, 0≤n1≤0.1, 0.05≤m1+n1≤0.1, m1 and n1 are not both 0, and x1+y1+z1+m1+n1=1.

[0050] According to some embodiments of the present invention, preferably, the positive electrode material B has the composition shown in Formula II:

[0051] Na a2 (Ni x2 Fe y2 Mn z2 M m2 M′ n2 O2 type II;

[0052] In the formula, 0.50≤a2≤1.10, 0≤x2≤0.5, 0≤y2≤0.5, 0≤z2≤0.5, 0≤m2≤0.1, 0≤n2≤0.1, 0.05≤m2+n2≤0.1, m2 and n2 are not both 0, and x2+y2+z2+m2+n2=1.

[0053] According to some embodiments of the present invention, preferably, in Formula I and Formula II, M is selected from at least one element selected from Cu, Co, V, Cr, Ti, Mg, Sn, Zn, Al, Zr, Nb, Y, W, and La, and M′ is selected from at least one element selected from Li, Al, Mg, Ti, Zr, Sr, La, Nb, B, and W.

[0054] According to some embodiments of the present invention, preferably, a1:(x1+y1+z1+m1+n1)=0.5-0.8:1, more preferably 0.6-0.80:1, and more preferably 0.67-0.8:1.

[0055] According to some embodiments of the present invention, preferably, a2:(x2+y2+z2+m2+n2)=0.7-1.1:1, more preferably 0.8-1.05:1, and more preferably 0.8-1:1.

[0056] According to some embodiments of the present invention, preferably, the difference between a2 and a1 is 0-0.5, more preferably 0.2-0.35. Using the above preferred embodiments is beneficial for obtaining the optimal combination of cathode material A (P2-type single crystal particles or P2 / O3-type single crystal particles) and cathode material B (P2 / O3-type aggregates or O3-type aggregates), further improving the capacity, rate capability, and cycle performance of the sodium-ion battery cathode material.

[0057] According to some embodiments of the present invention, preferably, the 2θ angle of the characteristic diffraction peaks of the (002) crystal planes of both cathode material A and cathode material B is greater than or equal to 15.7°, and the 2θ angle of the characteristic diffraction peaks of the (003) crystal planes of both cathode material A and cathode material B is less than or equal to 16.7°. Using the above preferred embodiments, in both cathode material A and cathode material B, n(Na) / n(Me) is between 0.5 and 1.1, thereby exhibiting better rate performance and capacity.

[0058] According to some embodiments of the present invention, the positive electrode material A has a relatively wide Na content range. + Transport channels and abundant sodium vacancies, Na + Direct diffusion is possible between two adjacent triangular prism sites, resulting in good rate performance of the sodium-ion battery cathode material; the high n(Na) / n(Me) ratio of the cathode material B results in high capacity of the sodium-ion battery cathode material.

[0059] According to some embodiments of the present invention, preferably, the ratio of the peak intensity of the characteristic diffraction peak of the (002) crystal plane to the peak intensity of the strongest diffraction peak is defined as I. A The ratio of the peak intensity of the characteristic diffraction peak of the (003) crystal plane to the peak intensity of the strongest diffraction peak is I. B The positive electrode material A satisfies: 0.4 ≤ I A / (I A +I B The positive electrode material B satisfies 0 ≤ I ≤ 1.0; A / (I A +I B ≤0.4. Using the above preferred embodiments, the single-crystal cathode material A can significantly improve the Na-ion transport rate and maintain the integrity of the layered structure, while the agglomerated cathode material B can release more sodium ions, resulting in better synergy in the electrochemical performance of the sodium-ion battery cathode materials.

[0060] The second aspect of the present invention provides a method for preparing the sodium-ion battery cathode material described in the first aspect, the method comprising: mixing cathode material A and cathode material B.

[0061] According to some embodiments of the present invention, preferably, the method for preparing the positive electrode material A includes:

[0062] (1) In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant and a complexing agent are mixed to carry out a first coprecipitation reaction to obtain precursor I;

[0063] (2) The precursor I is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and then sintered for the first time to obtain the cathode material A.

[0064] According to some embodiments of the present invention, preferably, the method for preparing the positive electrode material B includes:

[0065] (a) In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant and a complexing agent are mixed to carry out a second coprecipitation reaction to obtain precursor II;

[0066] (b) The precursor II is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and then subjected to a second sintering to obtain the cathode material B.

[0067] According to some embodiments of the present invention, preferably, the precursor I in step (1) and / or the precursor II in step (a) have a spherical or near-spherical morphology. More preferably, both the precursor I in step (1) and the precursor II in step (a) are spherical.

[0068] According to some embodiments of the present invention, preferably, the D of the precursor I and the precursor II... 50 The value range is 1-20μm.

[0069] According to some embodiments of the present invention, preferably, the particle size corresponding to 10% of the volume distribution of the precursor obtained by particle size testing is defined as D. 10 The particle size corresponding to 50% volume distribution is D. 50 The particle size corresponding to 90% volume distribution is D. 90 And define the homogeneity of the precursor as K. 90 And K 90 =(D 90 -D 10 ) / D 50 K of the precursor I and / or the precursor II 90 <1.0, narrow particle size distribution.

[0070] Using the above-mentioned preferred embodiments is beneficial for preparing cathode materials A and B with relatively uniform particle size, resulting in better gradation effect and higher compaction density in subsequent blending processes.

[0071] According to a preferred embodiment of the present invention, both precursor I in step (1) and precursor II in step (a) are spherical, and their K... 90 <1.0, D 50 The value range is 1-20μm.

[0072] According to some embodiments of the present invention, preferably, in step (2), the median particle size D of the positive electrode material A is... 50 The size is 1-5 μm, preferably 2-4 μm, and more preferably 3.6-4 μm.

[0073] According to some embodiments of the present invention, preferably, in step (2), the amount of sodium source used, according to stoichiometry, satisfies the following: n(Na) / n(Me) is 0.5-0.85, preferably 0.6-0.85.

[0074] According to some embodiments of the present invention, preferably, in step (b), the median particle size D of the positive electrode material B is... 50 The micrometer size is 6-16 μm, preferably 8-14 μm, and more preferably 12.3-13.9 μm.

[0075] According to some embodiments of the present invention, preferably, in step (b), the amount of sodium source used, according to stoichiometry, satisfies the following: n(Na) / n(Me) is 0.7-1.1, preferably 0.8-1.05.

[0076] According to some embodiments of the present invention, the nickel source, iron source, and manganese source can be soluble nickel sources, soluble iron sources, and soluble manganese sources conventionally used in the art, and there are no particular limitations thereto. Preferably, the nickel source, iron source, and manganese source are selected from at least one of sulfates, nitrates, and chlorides containing Ni, Fe, and Mn.

[0077] According to some embodiments of the present invention, the precipitant can be a precipitant conventionally used in the art, and there are no particular limitations thereto. Preferably, the precipitant is at least one selected from NaOH, KOH, and LiOH. The concentration of the precipitant can be 3-10 mol / L.

[0078] According to some embodiments of the present invention, the complexing agent can be a complexing agent conventionally used in the art, and there are no particular limitations thereto. Preferably, the complexing agent is at least one of ammonia, ammonium bicarbonate, ammonium carbonate, citric acid, and disodium ethylenediaminetetraacetate. The concentration of the complexing agent can be 2-11 mol / L.

[0079] According to some embodiments of the present invention, the sodium source can be a soluble sodium salt commonly used in the art, and there are no particular limitations thereto. Preferably, the sodium source is selected from at least one of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium oxide.

[0080] According to some embodiments of the present invention, preferably, the dopant containing M is selected from at least one of oxides, phosphates, fluorides, chlorides, hydroxides and silicides containing M, and more preferably from at least one of CuO, Co(OH)2, V2O5, Cr2O3, TiO2, MgCO3, Sr(OH)2, SrCO3, Al2O3, AlPO4, AlCl3, ZrO, Zr(HPO4)2, ZrSi2, Nb2O5, Y2O3, WO3, NaF3 and La2O3.

[0081] According to some embodiments of the present invention, preferably, the dopant containing M′ is selected from at least one of oxides, phosphates, carbonates, fluorides, chlorides, hydroxides and silicides containing M′, and more preferably from at least one of Li2CO3, Al2O3, AlPO4, AlCl3, MgO, Mg3(PO4)2, MgCO3, MgSi2, MgF2, MgCl2, TiO2, ZrO, Zr(HPO4)2, ZrSi2, Sr(OH)2, SrCO3, SrSi2, SrF2, SrCl2, La2O3, Nb2O5, B2O3 and WO3.

[0082] According to some embodiments of the present invention, preferably, the coprecipitation method used in the first coprecipitation reaction and / or the second coprecipitation reaction is a batch method, specifically including: feeding the nickel source, iron source, manganese source, precipitant, and complexing agent into the reaction vessel using a metering pump within a certain time period, and discharging the precipitate after it has fully crystallized and grown in the reaction vessel. Using a batch method for coprecipitation reaction is beneficial for obtaining precursors with a narrower particle size distribution.

[0083] According to some embodiments of the present invention, preferably, the conditions for the first coprecipitation reaction and / or the second coprecipitation reaction include: pH value of 10.0-12.5, temperature of 40-80℃, time of 48-120h, and stirring speed of 100-800rpm.

[0084] According to some embodiments of the present invention, preferably, the first sintering and / or the second sintering are carried out in an oxidizing atmosphere, and the conditions for the first sintering and / or the second sintering include: a temperature of 600-1200°C, a time of 10-20 h, and a heating rate of 0.5-10°C / min.

[0085] According to some embodiments of the present invention, preferably, the temperature of the second sintering is lower than the temperature of the first sintering.

[0086] According to some embodiments of the present invention, preferably, in step (2), the first sintering includes a first heating stage, a second heating stage and a first holding stage; the oxygen concentration in the atmosphere of the first heating stage is less than the oxygen concentration in the atmosphere of the second heating stage, and the heating rate of the first heating stage is greater than the heating rate of the second heating stage.

[0087] More preferably, the difference between the oxygen concentration in the atmosphere during the second heating stage and the oxygen concentration in the atmosphere during the first heating stage is 10-100 vol%.

[0088] More preferably, the difference between the heating rate of the first heating stage and the heating rate of the second heating stage is 2-15℃ / min.

[0089] The above-described preferred embodiments are beneficial to significantly improve the compaction density and structural stability of the sodium-ion battery cathode material obtained by mixing.

[0090] According to a preferred embodiment of the present invention, in step (2), the first sintering includes:

[0091] (2-1) First heating stage: In an oxygen-deficient atmosphere with an oxygen concentration ≤10 vol%, the temperature is increased to T1℃ at a first heating rate of ≥3℃ / min;

[0092] (2-2) Second heating stage: In an atmosphere with an oxygen concentration ≥20 vol%, the temperature is increased to T2℃ at a second heating rate of ≤2℃ / min;

[0093] (2-3) First heat preservation stage: heat preservation for t1 hours within the temperature range of T2-10℃ to T2+10℃;

[0094] Where T1 is in the range of 600℃≤T1≤800℃; T2 is the temperature of the first sintering, 900℃≤T2≤1100℃; t1 is the holding time, 5h≤t1≤15h.

[0095] According to some embodiments of the present invention, in step (2), the difference between the heating rate of the first heating stage and the heating rate of the second heating stage is 2-15℃ / min, 600℃≤T1≤800℃, 900℃≤T2≤1100℃, and 5h≤t1≤15h, which is beneficial to the formation of small-particle single-crystal material A. This structure can be added to the positive electrode material A with P2 or P2 / O3 type crystal structure, minimizing the phase transition in the entire wide potential region, alleviating the structural damage of layered oxides under high voltage, and ensuring high rate and high capacity output while maintaining high structural stability and good cycle stability.

[0096] According to some embodiments of the present invention, preferably, in step (b), the second sintering includes a third heating stage, a fourth heating stage, and a second holding stage; the oxygen concentration in the atmosphere of the third heating stage is less than the oxygen concentration in the atmosphere of the fourth heating stage, and the heating rate of the third heating stage is greater than the heating rate of the fourth heating stage.

[0097] More preferably, the difference between the oxygen concentration in the atmosphere during the fourth heating stage and the oxygen concentration in the atmosphere during the third heating stage is 10-100 vol%.

[0098] More preferably, the difference between the heating rate of the third heating stage and the heating rate of the fourth heating stage is 2-10℃ / min.

[0099] The above-described preferred embodiments are beneficial to significantly improve the compaction density and structural stability of the sodium-ion battery cathode material obtained by mixing.

[0100] According to a preferred embodiment of the present invention, in step (b), the second sintering includes:

[0101] (b-1) Third heating stage: In an oxygen-deficient atmosphere with an oxygen concentration ≤10 vol%, the temperature is increased to T3℃ at a third heating rate of ≥3℃ / min;

[0102] (b-2) Fourth heating stage: In an atmosphere with an oxygen concentration ≥20 vol%, the temperature is increased to T4℃ at a fourth heating rate of ≤2℃ / min;

[0103] (b-3) Second heat preservation stage: heat preservation for t2 hours within the temperature range of T4-10℃ to T4+10℃;

[0104] Wherein, T3 is in the range of 600℃≤T3≤800℃; T4 is the temperature of the second sintering, 800℃≤T4≤900℃; t2 is the holding time, 5h≤t2≤15h.

[0105] According to some embodiments of the present invention, in step (b), the difference between the heating rate of the third heating stage and the heating rate of the fourth heating stage is 2-10℃ / min, 600℃≤T3≤800℃, 800℃≤T4≤900℃; 5h≤t2≤15h, which is beneficial to the formation of large particle agglomerates of cathode material B. This structure can add with cathode material B having an O3 or O3 / P2 type crystal structure, minimizing the phase transition in the entire wide potential region, alleviating the structural damage of layered oxides under high voltage, and ensuring high rate and high capacity output while maintaining high structural stability and good cycle stability.

[0106] According to a particularly preferred embodiment of the present invention, the method for preparing the sodium-ion battery cathode material includes:

[0107] S1. In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant, and a complexing agent are mixed to carry out a first coprecipitation reaction to obtain precursor I;

[0108] S2. The precursor I is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and subjected to a first sintering to obtain cathode material A;

[0109] S3. In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant, and a complexing agent are mixed to carry out a second coprecipitation reaction to obtain precursor II;

[0110] S4. The precursor II is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and then sintered for a second time to obtain the cathode material B.

[0111] S5. Mix the positive electrode material A and the positive electrode material B.

[0112] The third aspect of this invention provides the application of the sodium-ion battery cathode material described in the first aspect, or the preparation method described in the second aspect, in a sodium-ion battery.

[0113] A fourth aspect of the present invention provides a sodium-ion battery, wherein the sodium-ion battery contains the sodium-ion battery positive electrode material described in the first aspect.

[0114] According to some embodiments of the present invention, the sodium-ion battery further includes a negative electrode and an electrolyte. There is no particular limitation on the type of negative electrode and the electrolyte; conventional types of negative electrodes and electrolytes in the art can be used, for example, the electrolyte can be a common commercial electrolyte.

[0115] The present invention will be described in detail below through embodiments.

[0116] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products.

[0117] In the following examples and comparative examples, the relevant parameters were obtained through testing using the following methods:

[0118] (1) The composition of the positive electrode material was determined by ICP method; the instrument used was PE Optima 7000DV, and the test conditions were that 0.1g of sample was completely dissolved in a mixed acid solution of 3mL HNO3 + 9mL HCl, and diluted to 250mL for testing;

[0119] (2) The morphology of the material was observed by scanning electron microscopy (SEM). The instrument used was a Hitachi S-4800 scanning electron microscope from Japan.

[0120] (3) The particle size of the cathode material was measured using a Malvern particle size analyzer;

[0121] (4) The crystal structure of the cathode material was tested by XRD. The instrument used was an X-ray diffractometer (Rigaku, SmartLab 9KW). The test conditions were: the X-ray source was Cu Kα rays, the scanning range was 10°-80°, the scanning rate was 1° / min, and the scanning step size was 0.02°.

[0122] (5) The powder compaction density of the positive electrode material was measured by the powder compaction method; the instrument used was a powder compactor (MCP-PD51), and the test conditions were 20KN.

[0123] (6) Electrochemical performance test: In the following examples and comparative examples, the electrochemical performance of the cathode material was tested using an R2025 coin cell sodium-ion battery.

[0124] The specific preparation process of sodium-ion batteries is as follows:

[0125] Electrode preparation: Sodium-ion battery positive electrode material, conductive agent SuperP and polyvinylidene fluoride (PVDF) are thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 90:5:5 to form a uniform slurry. The slurry is coated on aluminum foil and dried at 120°C for 12 hours. Then, it is pressed into shape using a pressure of 100 MPa to produce a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm.

[0126] Battery Assembly: In an argon-filled glove box with both water and oxygen content less than 5 ppm, the positive electrode, separator, negative electrode, and electrolyte were assembled into an R2025 coin-type sodium-ion battery and then allowed to stand for 6 hours. The negative electrode used a 14 mm diameter, 1 mm thick metallic sodium sheet; the separator used a 25 μm thick coated separator; and the electrolyte was a 4:6 mixture of 1 mol / L NaPF6, ethyl methyl carbonate (EMC), and propylene carbonate (PC).

[0127] Electrochemical performance testing:

[0128] In the following examples and comparative examples, the electrochemical performance of R2025 coin cell sodium-ion batteries was tested using the Shenzhen Xinwei Battery Testing System (CT3008). The initial charge-discharge capacity test conditions were 0.1C@2-4.0V, 25℃, with a constant voltage cutoff current of 0.02C; the cycle performance test conditions were 1.0C@2-4.0V, 25℃. The coin cell sodium-ion batteries were subjected to constant current charge-discharge tests at 0.1C and 1C to evaluate the charge-discharge specific capacity, cycle performance, and volumetric energy density of the sodium-ion battery cathode material. A higher capacity retention rate during cycling indicates higher material stability and better cycle performance of the battery system.

[0129] Example 1

[0130] S1: Dissolve nickel sulfate, ferric sulfate, and manganese sulfate in a molar ratio of nickel, iron, and manganese of 20:40:40 to obtain a 2 mol / L mixed salt solution; dissolve sodium hydroxide to obtain an 8 mol / L precipitant solution; and dissolve ammonia to obtain a 10.4 mol / L complexing agent solution.

[0131] 100L of mixed salt solution, precipitant solution, and complexing agent solution were introduced into the reactor in a co-flow manner to carry out the first coprecipitation reaction. Then, under the protection of argon atmosphere, the crystal growth reaction was carried out continuously. The obtained precursor slurry was filtered, washed, and the filter cake was dried at 120℃ and then sieved to obtain precursor I.

[0132] The conditions for the first coprecipitation reaction were: pH 12.38, temperature 60℃, time 80 h, and stirring speed 700 rpm; the D of precursor I... 50 and K 90 See Table 1;

[0133] S2: The above precursor I is mixed with Na2CO3, CuO and Sr(OH)2 for the first sintering. The sintered product is then cooled, crushed and sieved to obtain cathode material A, with a median particle size D. 50 See Table 4;

[0134] Table 1 shows the amount of sodium source (i.e., n(Na) / n(Ni+Fe+Mn+M+M′)) and the crystal form of cathode material A, based on stoichiometry.

[0135] The first sintering is carried out in an oxygen atmosphere, and the specific steps of the first sintering are as follows:

[0136] First heating stage: In an oxygen-deficient atmosphere with an oxygen concentration of 5 vol%, the temperature is increased to 700℃ at a first heating rate of 3℃ / min.

[0137] Second heating stage: In an atmosphere with an oxygen concentration of 20 vol%, the temperature is increased to 900℃ at a second heating rate of 1℃ / min;

[0138] First heat preservation stage: heat preservation for 15 hours within a temperature range of 890℃ to 910℃;

[0139] S3: Following the steps in S1, 100L of mixed salt solution, precipitant solution, and complexing agent solution are introduced into the reactor in a co-current manner to carry out the second coprecipitation reaction. Then, under the protection of argon atmosphere, the crystal growth reaction is continuously carried out. The obtained precursor slurry is filtered, washed, and the filter cake is dried at 120℃ and then sieved to obtain precursor II.

[0140] The conditions for the second coprecipitation reaction were: pH 12.10, temperature 60℃, time 80 h, and stirring speed 400 rpm; the D of precursor II... 50 and K 90 See Table 1;

[0141] S4: The above precursor II is mixed with Na2CO3, CuO and Sr(OH)2 for a second sintering. The sintered product is then cooled, crushed and sieved to obtain cathode material B, with a median particle size D. 50 See Table 4;

[0142] Table 1 shows the amount of sodium source (i.e., n(Na) / n(Ni+Fe+Mn+M+M′)) and the crystal form of cathode material B, based on stoichiometry.

[0143] The second sintering is carried out in an oxygen atmosphere, and the specific steps of the second sintering are as follows:

[0144] The third heating stage: In an oxygen-deficient atmosphere with an oxygen concentration of 5 vol%, the temperature is increased to 700℃ at a third heating rate of 3.5℃ / min.

[0145] Fourth heating stage: In an atmosphere with an oxygen concentration of 20 vol%, the temperature is increased to 850℃ at a fourth heating rate of 1.5℃ / min;

[0146] Second heat preservation stage: heat preservation for 10 hours within the temperature range of 840℃ to 860℃;

[0147] S5: Mix the cathode material A prepared in S2 with the cathode material B prepared in S4 (the weight ratio of the two is shown in Table 1) to obtain the cathode material for sodium-ion batteries.

[0148] Example 2

[0149] The method of Example 1 is the same except that the ratio of n(Na) / n(Me) in step S4 is different, resulting in P2 / O3 type agglomerated cathode material B (see Table 1 for details). The rest are the same, resulting in sodium-ion battery cathode material.

[0150] Example 3

[0151] The method of Example 1 is the same except that the ratio of n(Na) / n(Me) in step S2 is different, resulting in P2 / O3 type single crystal cathode material A (see Table 1 for details). The rest are the same, resulting in sodium-ion battery cathode material.

[0152] Example 4

[0153] The method of Example 3 is followed, except that in step S5, the weight ratio of positive electrode material A to positive electrode material B (see Table 1 for details) is the same, and all other parameters are the same, to obtain the positive electrode material for sodium-ion batteries.

[0154] Example 5

[0155] The method of Example 3 is followed, except that in steps S2 and S4, the dopant containing M is TiO2 and the dopant containing M′ is B2O3, and the rest are the same, to obtain a sodium-ion battery cathode material.

[0156] Example 6

[0157] The method is the same as in Example 3, except that the median particle size D of precursor I in step S1 and precursor II in step S3 is different. 50 (See Table 1 for details), and all other aspects are the same, thus obtaining the positive electrode material for sodium-ion batteries.

[0158] Example 7

[0159] The method of Example 3 is followed, except that in step S5, the weight ratio of positive electrode material A to positive electrode material B (see Table 1 for details) is the same, and all other parameters are the same, to obtain the positive electrode material for sodium-ion batteries.

[0160] Example 8

[0161] The method is the same as in Example 3, except that the median particle size D of precursor I in step S1 and precursor II in step S3 is different. 50 (See Table 1 for details) and the median particle size D of cathode material A and cathode material B obtained. 50 (See Table 4 for details), and the rest are the same, thus obtaining the sodium-ion battery cathode material.

[0162] Comparative Example 1

[0163] Following the method of Example 1, the difference is that in step S2, the amount ratio of n(Na) / n(Me) is different, resulting in O3 type single crystal cathode material A; in step S4, the amount ratio of n(Na) / n(Me) is different, resulting in P2 type agglomerated cathode material B; see Table 1 for details, the rest are the same, resulting in sodium-ion battery cathode material.

[0164] Comparative Example 2

[0165] The method of Example 3 is different in that, in step S4, the third heating stage heats up to 700°C at a third heating rate of 3°C / min; the fourth heating stage heats up to 900°C at a fourth heating rate of 1°C / min; and the second holding stage holds at a temperature range of 890°C to 910°C for 15 hours; thereby obtaining O3 type single crystal cathode material B (see Table 1 for details). The rest are the same, and sodium-ion battery cathode material is obtained.

[0166] Table 1

[0167]

[0168]

[0169] Note: a2-a1 * That is, the difference between a2 and a1 in the chemical formula of the cathode material.

[0170] The compositions of the cathode materials prepared in the above embodiments and comparative examples are shown in Table 2.

[0171] Table 2

[0172]

[0173]

[0174] Test case

[0175] (1) Morphological test

[0176] This invention tested scanning electron microscope (SEM) images of precursor I, precursor II, cathode material A, cathode material B, and sodium-ion battery cathode material prepared in the above embodiments and comparative examples, and exemplarily provides SEM images of precursor I, precursor II, cathode material A, cathode material B, and sodium-ion battery cathode material prepared in Example 1. The results are as follows: Figure 1-5 As shown, from Figure 1 and Figure 2 It can be seen that precursor I has small, round particles with a loose surface; precursor II has a dense surface; from Figure 3 It can be seen that the degree of single crystallization of cathode material A is good, and its surface is smooth and rounded; from Figure 4It can be seen that the surface of the agglomerated cathode material B is rounded and dense. From Figure 5 As can be seen, in the sodium-ion battery cathode material of the present invention, single-crystal cathode material A and agglomerated cathode material B are mixed, and small particles fill the spaces between large particles, exhibiting good gradation performance.

[0177] (2) Physical property testing

[0178] This invention tested the XRD patterns of P2-type single-crystal cathode material A, P2 / O3-type single-crystal cathode material A, P2 / O3-type agglomerated cathode material B, and O3-type agglomerated cathode material B in the above embodiments and comparative examples, and provided exemplary XRD images of P2-type single-crystal cathode material A, O3-type agglomerated cathode material B prepared in Example 1, and P2 / O3-type agglomerated cathode material B prepared in Example 2. The results are as follows: Figure 6-8 As shown.

[0179] The XRD characteristic diffraction peak parameters of the cathode materials prepared in the above embodiments and comparative examples are shown in Table 3.

[0180] Table 3

[0181]

[0182]

[0183] This invention tested the median particle size D of the cathode material A, cathode material B, and sodium-ion battery cathode material prepared in the above embodiments and comparative examples. 50 The compaction density is shown in Table 4.

[0184] Table 4

[0185]

[0186]

[0187] The above results show that the K90 of precursor I and precursor II obtained by the method described in this application is less than 1, and the particle size distribution is narrow. Figure 1-4 It can be further observed that the obtained cathode material A and cathode material B have relatively uniform particle sizes. Among them, when the median particle size D of cathode material A and cathode material B is relatively uniform... 50 When the value range of the positive electrode material and the mixing ratio of positive electrode material A and positive electrode material B are within the preferred range, that is, when the particle size distribution of the multiphase composite oxide and the content ratio of each composite phase are within the preferred range by hierarchical control, the compaction density of the material and the volumetric energy density of the electrode can be improved (corresponding to Table 5).

[0188] (3) Electrochemical performance testing

[0189] The present invention tested the electrochemical performance of the sodium-ion battery cathode materials prepared in the above embodiments and comparative examples, including the 0.1C initial discharge specific capacity, 1C discharge specific capacity, rate performance, cycle performance and volumetric energy density. The specific test results are shown in Table 5.

[0190] Table 5

[0191]

[0192]

[0193] The above results show that the sodium-ion battery cathode material provided by this invention, when combining P2, P2 / O3, or O3 crystal forms with single crystals or agglomerates in the specific form described in this application, exhibits better rate performance and cycle performance, and can synergistically improve electrochemical performance, significantly enhancing the electrochemical performance of the sodium-ion battery cathode material. Furthermore, by further limiting the mixing ratio of cathode material A and cathode material B, and the median particle size of cathode material A and cathode material B, the compaction density of the sodium-ion cathode material can be further increased, mitigating the structural damage of layered oxides under high voltage. Additionally, doping elements can further improve the rate performance and cycle performance of the sodium-ion battery cathode material. Wherein:

[0194] Comparing Example 1 and Comparative Example 1, and Comparative Example 3 and Comparative Example 2, it can be seen that when the cathode material A is a single crystal particle and has a characteristic diffraction peak of the (002) crystal plane at 2θ of 14°-18°, and the cathode material B is an agglomerate and has a characteristic diffraction peak of the (003) crystal plane at 2θ of 14°-18°, it has better rate performance and cycle performance. In other words, the sodium-ion cathode material provided by the present invention contains cathode material A and cathode material B. Cathode material A at least exhibits the crystal characteristics of P2 type and has the performance of single crystal particles, while cathode material B at least exhibits the crystal characteristics of O3 type and exhibits the performance of agglomerated particles. Compared with the sodium-ion battery cathode material containing O3 type single crystal cathode material A and P2 type agglomerated cathode material B, the sodium-ion cathode material formed by mixing cathode material A and cathode material B with the characteristics described above has comprehensive performance that balances high capacity and long cycle life, as well as higher volumetric energy density.

[0195] Comparing the test results of Example 1 and Example 2, it can be seen that, compared with O3-type agglomerated cathode material B, the P2 / O3-type composite phase agglomerated cathode material B, after being mixed with P2-type single crystal cathode material A, can further enhance the structural stability of sodium-ion battery cathode materials and further improve their rate performance and cycle performance.

[0196] Comparing the test results of Example 1 and Example 3, it can be seen that, compared with P2 type single crystal cathode material A, the mixing of P2 / O3 type composite phase single crystal cathode material A with O3 type agglomerated cathode material B can further enhance the capacity and volumetric energy density of sodium-ion battery cathode materials on the basis of stable rate performance and cycle performance.

[0197] Comparing the test results of Example 3 and Example 5, it can be seen that different combinations of doping elements in the sodium-ion battery cathode material can further enhance the stability of the single crystal structure and further improve the cycle performance and rate performance of the sodium-ion battery cathode material.

[0198] Comparing the test results of Examples 3-4 and Example 7, it can be seen that the contents of cathode material A and cathode material B in the sodium-ion battery cathode material are within the preferred range defined by the present invention, which further improves the compaction density of the sodium-ion battery cathode material.

[0199] Comparing the test results of Examples 3, 6, and 8, it can be seen that the median particle size D of cathode material A and cathode material B is... 50 Within the preferred scope defined by this invention, it is possible to further improve the compaction density and volumetric energy density of sodium-ion battery cathode materials while maintaining stable rate performance and cycle performance.

[0200] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A sodium-ion battery cathode material, characterized in that, The sodium-ion battery cathode material comprises cathode material A and cathode material B; wherein, cathode material A is a single crystal particle with a P2 or P2 / O3 type crystal structure; and cathode material B is an aggregate with an O3 or P2 / O3 type crystal structure; and, In the XRD patterns of the cathode material A and the cathode material B, each independently has characteristic diffraction peaks of the (002) crystal plane and / or the (003) crystal plane at a 2θ of 14°-18°, and the 2θ angle of the characteristic diffraction peak of the (002) crystal plane is smaller than the 2θ angle of the characteristic diffraction peak of the (003) crystal plane. Wherein, the cathode material A has at least the characteristic diffraction peak of the (002) crystal plane, and the cathode material B has at least the characteristic diffraction peak of the (003) crystal plane; The cathode material A has the composition shown in Formula I: Na a1 (Ni x1 Fe y1 Mn z1 M m1 M′ n1 )O₂ of formula I; In the formula, 0.50≤a1≤1.10, 0≤x1≤0.5, 0≤y1≤0.5, 0≤z1≤0.5, 0≤m1≤0.5, 0≤n1≤0.1, 0.05≤m1+n1≤0.1, m1 and n1 are not both 0, and x1+y1+z1+m1+n1= 1; The cathode material B has the composition shown in Formula II: Na a2 (Ni x2 Fe y2 Mn z2 M m2 M′ n2 )O₂ of formula II; In the formula, 0.50≤a2≤1.10, 0≤x2≤0.5, 0≤y2≤0.5, 0≤z2≤0.5, 0≤m2≤0.1, 0≤n2≤0.1, 0.05≤m2+n2≤0.1, m2 and n2 are not both 0, and x2+y2+z2+m2+n2= 1; M is selected from at least one element chosen from Cu, Co, V, Cr, Ti, Mg, Sn, Zn, Al, Zr, Nb, Y, W, and La, and M′ is selected from at least one element chosen from Li, Al, Mg, Ti, Zr, Sr, La, Nb, B, and W.

2. The sodium-ion battery cathode material according to claim 1, wherein, The median particle size D of the cathode material A 50 1-5μm; And / or, the median particle size D of the cathode material B 50 It is 6-16 μm; And / or, the median particle size D of the sodium-ion battery cathode material 50 It ranges from 1 to 20 μm.

3. The sodium-ion battery cathode material according to claim 2, wherein, The median particle size D of the cathode material A 50 It is 2-4 μm.

4. The sodium-ion battery cathode material according to claim 3, wherein, The median particle size D of the cathode material A 50 It is 3.6-4μm.

5. The sodium-ion battery cathode material according to claim 2, wherein, The median particle size D of the cathode material B 50 It is 8-14μm.

6. The sodium-ion battery cathode material according to claim 5, wherein, The median particle size D of the cathode material B 50 It is 12.3-13.9 μm.

7. The sodium-ion battery cathode material according to claim 2, wherein, The median particle size D of the sodium-ion battery cathode material 50 It is 5-15μm.

8. The sodium-ion battery cathode material according to claim 1, wherein, The weight ratio of the positive electrode material A to the positive electrode material B is 1:0.1-9.

9. The sodium-ion battery cathode material according to claim 8, wherein, The weight ratio of the positive electrode material A to the positive electrode material B is 1:0.4-2.

5.

10. The sodium-ion battery cathode material according to claim 1, wherein, a1: (x1+y1+z1+m1+n1) = 0.5-0.8: 1; a2: (x2+y2+z2+m2+n2) = 0.7-1.1:

1.

11. The sodium-ion battery cathode material according to claim 10, wherein, a1: (x1+y1+z1+m1+n1) = 0.6-0.80: 1; a2: (x2+y2+z2+m2+n2) = 0.8-1.05:

1.

12. The sodium-ion battery cathode material according to claim 11, wherein, a1: (x1+y1+z1+m1+n1) = 0.67-0.8: 1; a2: (x2+y2+z2+m2+n2) =0.8-1:

1.

13. The sodium-ion battery cathode material according to claim 12, wherein, The difference between a2 and a1 is 0-0.

5.

14. The sodium-ion battery cathode material according to claim 13, wherein, The difference between a2 and a1 is 0.2-0.

35.

15. The sodium-ion battery cathode material according to claim 1, wherein, The ratio of the peak intensity of the characteristic diffraction peak to the peak intensity of the strongest diffraction peak of the (002) crystal plane is defined as I. A The ratio of the peak intensity of the characteristic diffraction peak of the (003) crystal plane to the peak intensity of the strongest diffraction peak is I. B The positive electrode material A satisfies: 0.4 ≤ I A / (I A +I B The positive electrode material B satisfies 0 ≤ I ≤ 1.0; A / (I A +I B ≤0.

4.

16. A method for preparing a sodium-ion battery cathode material according to any one of claims 1-15, characterized in that, The preparation method includes: Cathode material A and cathode material B are mixed.

17. The preparation method according to claim 16, wherein, The method for preparing the cathode material A includes: (1) In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant and a complexing agent are mixed to carry out a first coprecipitation reaction to obtain precursor I; (2) The precursor I is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and subjected to a first sintering to obtain the cathode material A; The method for preparing the cathode material B includes: (a) In the presence of a solvent, a nickel source, an iron source, a manganese source, a precipitant and a complexing agent are mixed to carry out a second coprecipitation reaction to obtain precursor II; (b) The precursor II is mixed with a sodium source, a dopant containing M and / or a dopant containing M′ and then subjected to a second sintering to obtain the cathode material B.

18. The preparation method according to claim 17, wherein, Both precursor I in step (1) and precursor II in step (a) are spherical, and their K... 90 <1.0; D 50 The value range is 1-20μm; In steps (2) and (b), the dopant containing M is each independently selected from at least one of oxides, phosphates, fluorides, chlorides, hydroxides and silicides containing M; Each of the M′-containing dopants is independently selected from at least one of the following: oxides, phosphates, carbonates, fluorides, chlorides, hydroxides, and silicides containing M′.

19. The preparation method according to claim 17, wherein, In step (2), the median particle size D of the cathode material A is... 50 It is 1-5μm.

20. The preparation method according to claim 19, wherein, In step (2), the median particle size D of the cathode material A is... 50 It is 2-4 μm.

21. The preparation method according to claim 20, wherein, In step (2), the median particle size D of the cathode material A is... 50 It is 3.6-4μm.

22. The preparation method according to claim 17, wherein, In step (2), the amount of sodium source used, according to the stoichiometric ratio, satisfies the following condition: n(Na) / n(Me) is 0.5-0.

85.

23. The preparation method according to claim 22, wherein, In step (2), the amount of sodium source used, according to the stoichiometric ratio, satisfies the following condition: n(Na) / n(Me) is 0.6-0.

85.

24. The preparation method according to claim 17, wherein, In step (b), the median particle size D of the cathode material B is... 50 It is 6-16μm.

25. The preparation method according to claim 24, wherein, In step (b), the median particle size D of the cathode material B is... 50 It is 8-14μm.

26. The preparation method according to claim 25, wherein, In step (b), the median particle size D of the cathode material B is... 50 It is 12.3-13.9 μm.

27. The preparation method according to claim 17, wherein, In step (b), the amount of sodium source used, according to stoichiometry, satisfies the following condition: n(Na) / n(Me) is 0.7-1.

1.

28. The preparation method according to claim 27, wherein, In step (b), the amount of sodium source used, according to stoichiometry, satisfies the following condition: n(Na) / n(Me) is 0.8-1.

05.

29. The preparation method according to claim 17, wherein, In steps (2) and (b), the sodium source is independently selected from at least one of sodium carbonate, sodium hydroxide, sodium nitrate and sodium oxide.

30. The preparation method according to claim 17, wherein, In steps (2) and (b), the dopant containing M is independently selected from at least one of CuO, Co(OH)2, V2O5, Cr2O3, TiO2, MgCO3, Sr(OH)2, SrCO3, Al2O3, AlPO4, AlCl3, ZrO, Zr(HPO4)2, ZrSi2, Nb2O5, Y2O3, WO3, NaF3 and La2O3; Each of the M′-containing dopants is independently selected from at least one of Li2CO3, Al2O3, AlPO4, AlCl3, MgO, Mg3(PO4)2, MgCO3, MgSi2, MgF2, MgCl2, TiO2, ZrO, Zr(HPO4)2, ZrSi2, Sr(OH)2, SrCO3, SrSi2, SrF2, SrCl2, La2O3, Nb2O5, B2O3, and WO3.

31. The preparation method according to any one of claims 17-30, wherein, The conditions for the first coprecipitation reaction and / or the second coprecipitation reaction include: pH value of 10.0-12.5, temperature of 40-80℃, time of 48-120h, and stirring speed of 100-800rpm.

32. The preparation method according to any one of claims 17-30, wherein, The first sintering and / or the second sintering are carried out in an oxidizing atmosphere, and the conditions for the first sintering and / or the second sintering include: a temperature of 600-1200℃, a time of 10-20h, and a heating rate of 0.5-10℃ / min.

33. The preparation method according to any one of claims 17-30, wherein, The temperature of the second sintering is lower than that of the first sintering.

34. The preparation method according to claim 33, wherein, The conditions for the first sintering include a temperature of 900-1100℃ and a time of 5-15h; the conditions for the second sintering include a temperature of 800-900℃ and a time of 5-15h.

35. The application of the sodium-ion battery cathode material according to any one of claims 1-15, or the preparation method according to any one of claims 16-34, in a sodium-ion battery.

36. A sodium-ion battery, characterized in that, The sodium-ion battery contains the sodium-ion battery cathode material as described in any one of claims 1-15.

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