Positive electrode material precursor and preparation method thereof, positive electrode material, positive electrode plate and sodium ion battery

Abstract

The invention provides a positive electrode material precursor and a preparation method thereof, a positive electrode material, a positive electrode plate and a sodium ion battery. The preparation method comprises the following steps: carrying out first precipitation reaction on a solution A, a complexing agent and a precipitator in a reaction kettle to obtain a first product; adding the solution B into the reaction kettle, and carrying out a second precipitation reaction to obtain a positive electrode material precursor; the solution A comprises a nickel source, an iron source and a manganese source, and the molar ratio of the nickel source to the iron source to the manganese source is (0.45-0.50): (0.20-0.25): (0.28-0.32); the solution B comprises a titanium source and an antimony source, and the molar ratio of the titanium source to the antimony source is (1.5-2.5): 1. Based on a coprecipitation method, the electrochemical activity of the precursor material is improved, and meanwhile, the structural stability of the subsequently obtained positive electrode material in the charging and discharging process is improved, so that the long cycle performance and the high power characteristic of the finally obtained battery are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion batteries, and more specifically, to a cathode material precursor and its preparation method, a cathode material, a cathode electrode sheet, and a sodium-ion battery. Background Technology

[0002] With the continuous innovation of new energy technologies, the requirements for energy conversion are constantly increasing in terms of technology, cost, efficiency, service life, and safety. Lithium-ion batteries, due to their high energy density, long cycle life, and good safety, have been widely used in portable electronic devices such as mobile phones and laptops, new energy vehicles, and energy storage systems. However, with the increasing scarcity of lithium resources, the development of a candidate battery to replace lithium-ion batteries has become urgent. Sodium-ion batteries (SIBs) have attracted widespread attention due to their similar working principle and cell manufacturing process to lithium-ion batteries, and the abundance of sodium resources. Layered transition metal oxide sodium-ion battery cathode materials with an O3 phase structure have high theoretical specific capacity, good conductivity, and great application potential.

[0003] Similar to layered oxide cathode materials in lithium-ion batteries, layered oxide cathode materials for sodium-ion batteries (such as transition metal oxides with an O3 phase structure) have also attracted attention due to their high theoretical specific capacity and good conductivity. However, the extraction and insertion processes of sodium ions in these materials are often accompanied by significant volume changes and structural rearrangements, leading to a decrease in the material's cycle stability and rate performance. Furthermore, the reaction between high-voltage electrolytes and the cathode material surface, as well as stability issues in air, are also important factors hindering the commercialization of sodium-ion batteries.

[0004] Meanwhile, precursor preparation is a crucial step in cathode material synthesis, directly impacting the final material's chemical composition, particle morphology, and performance. Coprecipitation, a mature and widely used wet chemical synthesis technique, is the preferred method for preparing high-performance cathode material precursors due to its ability to effectively control the uniform distribution of metal ions, as well as particle morphology and size. In cathode material synthesis, coprecipitation is typically used to react metal salts (such as nickel, iron, and manganese salts) with complexing agents (such as ammonia) and precipitants (such as sodium hydroxide) in a reactor to generate hydroxide precursors with specific stoichiometric ratios and morphologies. This method ensures a uniform distribution of metal elements, facilitating the synthesis of highly consistent materials and thus improving battery cycle stability and rate performance. However, traditional coprecipitation processes often struggle to control the distribution of metal elements on the particle surface, leading to structural phase transitions during charge and discharge, which negatively impacts the material's electrochemical performance.

[0005] Therefore, how to provide a method for preparing a cathode material precursor based on co-precipitation, so that the obtained precursor can exhibit superior electrochemical performance and cycle stability after the cathode material is prepared, is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to provide a cathode material precursor and its preparation method, a cathode material, a cathode electrode sheet, and a sodium-ion battery, in order to solve the problems of low operating voltage, low reversible capacity, and poor cycle performance of cathode materials in the prior art.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a cathode material precursor, comprising: step S1, wherein solution A, a complexing agent, and a precipitant undergo a first precipitation reaction in a reactor to obtain a first product with a D50 of 3.5 μm to 4.5 μm; step S2, wherein solution B is added to the reactor, and a second precipitation reaction is performed to obtain the cathode material precursor; solution A includes a nickel source, an iron source, and a manganese source, and the molar ratio of the nickel source, the iron source, and the manganese source is (0.45~0.50):(0.20~0.25):(0.28~0.32); solution B includes a titanium source and an antimony source, and the molar ratio of the titanium source and the antimony source is (1.5~2.5):1.

[0008] Further, in step S1-1, the nickel source, iron source, and manganese source are prepared into solution A, the complexing agent is prepared into a complexing agent solution, and the precipitant is prepared into a precipitant solution; in step S1-2, solution A, the complexing agent solution, and the precipitant solution are flowed into a reaction vessel, and a first precipitation reaction is carried out under the condition of pH 10.5~11.5 to obtain a reaction solution containing the first product; in step S2-1, the titanium source and antimony source are prepared into solution B; in step S2-2, under the condition that solution A, the complexing agent solution, and the precipitant solution are kept flowing in, solution B is flowed into a reaction vessel containing the reaction solution, and a second precipitation reaction is carried out to obtain the cathode material precursor.

[0009] Furthermore, the flow rate ratio of solution A, complexing agent solution, and precipitant solution is 1:(0.85~0.95):(0.85~0.95); the flow rate ratio of solution B, complexing agent solution, and precipitant solution is 1:(0.85~0.95):(0.85~0.95); the flow rate of solution A is 1.0L / h~3.0L / h, and the flow rate of solution B is 0.5L / h~1.5L / h.

[0010] Further, in solution A, the total molar concentration of metal ions is 1.0 mol / L to 1.5 mol / L; and / or, in solution B, the total molar concentration of metal ions is 0.4 mol / L to 0.6 mol / L; and / or, in the complexing agent solution, the molar concentration of the complexing agent is 3.5 mol / L to 4.5 mol / L; and / or, in the precipitating agent solution, the molar concentration of the precipitating agent is 4.5 mol / L to 5.5 mol / L; preferably, the complexing agent is selected from one or more of ammonia water, ammonium sulfate, ammonium chloride, and citric acid, more preferably ammonia water; the precipitating agent is selected from one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate, more preferably sodium hydroxide.

[0011] Further, both step S1 and step S2 are carried out under stirring conditions, and the stirring speed is 400 rpm to 500 rpm; and / or, step S1 and step S2 are each independently carried out at 55 °C to 65 °C; and / or, both step S1 and step S2 are carried out in a protective atmosphere, and the protective atmosphere is nitrogen and / or argon.

[0012] Further, the nickel source, iron source, manganese source, titanium source, and antimony source are each independently added in the form of acetate, sulfate, nitrate, and chloride; preferably, the nickel source is selected from one or more of nickel acetate, nickel sulfate, nickel chloride, and nickel nitrate; and / or, the iron source is selected from one or more of ferric sulfate, ferric chloride, ferric nitrate, ferrous sulfate, ferrous chloride, ferrous nitrate, and ferrous acetate; and / or, the manganese source is selected from one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; and / or, the titanium source is titanium sulfate and / or titanium chloride; and / or, the antimony source is antimony chloride and / or antimony nitrate.

[0013] The second aspect of the present invention provides a cathode material precursor, which is prepared by the preparation method of the above cathode material precursor, and the chemical formula of the cathode material precursor is Ni y Fe 0.2 [[ID=​​​​​​​​​​​​​​​​​​​

[0015] A fourth aspect of the present invention provides a positive electrode sheet comprising the aforementioned positive electrode material.

[0016] A fifth aspect of the present invention provides a sodium-ion battery comprising the aforementioned positive electrode.

[0017] By applying the technical solution of this invention, a Ni, Fe, and Mn matrix structure with a specific stoichiometric ratio is first prepared using a co-precipitation method. Then, a Ti / Sb mixed solution is introduced to ensure that the Ti / Sb elements are uniformly distributed on the particle surface, forming a protective shell. This enhances the stability of the obtained precursor material and the subsequently obtained cathode material against air and its resistance to H2O and CO2 corrosion. Furthermore, while improving the electrochemical activity of the precursor material, it also improves the structural stability of the subsequently obtained cathode material during charge and discharge processes, thereby ensuring the long-cycle performance and high-power characteristics of the final battery. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 The results are shown in the scanning electron microscope (SEM) characterization of the cathode material precursor obtained in Example 1 of this invention.

[0020] Figure 2 The above are the SEM characterization results of the cathode material obtained in Example 1 of this invention. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0022] As described in the background section, existing cathode materials suffer from low operating voltage, low reversible capacity, and poor cycle performance. To address these technical problems, a first aspect of the present invention provides a method for preparing a cathode material precursor, comprising: step S1, in which solution A, a complexing agent, and a precipitant undergo a first precipitation reaction in a reactor to obtain a first product with a D50 of 3.5 μm to 4.5 μm; step S2, in which solution B is added to the reactor, and a second precipitation reaction is performed to obtain the cathode material precursor; solution A includes a nickel source, an iron source, and a manganese source, and the molar ratio of the nickel source, iron source, and manganese source is (0.45~0.50):(0.20~0.25):(0.28~0.32); solution B includes a titanium source and an antimony source, and the molar ratio of the titanium source and the antimony source is (1.5~2.5):1.

[0023] This invention is based on a co-precipitation method. First, a Ni, Fe, and Mn matrix structure with a specific stoichiometric ratio is prepared. Then, a Ti / Sb mixed solution is introduced to ensure that Ti / Sb elements are uniformly distributed on the particle surface, forming a protective shell, thereby obtaining a structurally stable and high-performance cathode material precursor. More specifically, in the above preparation method, a Ni, Fe, and Mn matrix structure is first formed in solution A, and the D50 of this intermediate product is strictly controlled to be 3.5 μm to 4.5 μm. This ensures that Ti / Sb elements are uniformly coated onto the surface during the second precipitation reaction, avoiding uneven coating thickness due to excessively small particles or coating difficulties due to excessively large particles. In the second precipitation reaction stage, Ti and Sb elements further co-precipitate and form a co-coating layer, increasing the lattice stability and sodium ion diffusion efficiency of the obtained precursor material and the subsequently obtained cathode material. The introduction of Ti increases the lattice spacing and reduces the damage to the lattice during sodium ion insertion / extraction, while Sb enhances the binding force between metal ions and oxygen, stabilizes the cathode material structure, and reduces phase transitions during charge and discharge, thereby improving its cycle stability.

[0024] In several typical embodiments, preferred step S1 includes: step S1-1, preparing a nickel source, an iron source, and a manganese source into solution A, preparing a complexing agent into a complexing agent solution, and preparing a precipitant into a precipitant solution; step S1-2, flowing solution A, the complexing agent solution, and the precipitant solution into a reaction vessel, and carrying out a first precipitation reaction under conditions of pH 10.5~11.5 to obtain a reaction solution containing a first product; preferably, the flow rate ratio of solution A, the complexing agent solution, and the precipitant solution is 1:(0.85~0.95):(0.85~0.95). In the above preferred embodiment, by optimizing the flow rate ratio of solution A, the complexing agent solution, and the precipitant during introduction, the effective reaction between metal ions and the complexing agent can be promoted, forming a more uniform complexation state of metal ions, which is more conducive to subsequent uniform precipitation and reduces the chemical heterogeneity within the obtained precursor material. The pH range of 10.5 to 11.5 creates a more suitable alkaline environment, which can further optimize the precipitation of metal hydroxides, reduce the formation of excessive hydroxide by-products, and thus significantly improve the purity and crystal quality of the precipitate. Ultimately, this results in the preparation of a cathode material precursor with superior performance, which in turn significantly improves the performance of the subsequently obtained cathode material.

[0025] Further, preferred step S2 includes: step S2-1, preparing a solution B from titanium and antimony sources; step S2-2, under the condition that solution A, complexing agent solution, and precipitant solution are continuously flowing in, solution B is flowed into a reaction vessel containing the reaction liquid, and a second precipitation reaction is performed to obtain a cathode material precursor; preferably, the flow ratio of solution B, complexing agent solution, and precipitant solution is 1:(0.85~0.95):(0.85~0.95). In this preferred embodiment, Ti and Sb are prepared as a second solution, and their flow is controlled at a specific flow ratio in the first precipitation reaction, thereby promoting the more uniform coating of Ti / Sb elements on the surface of the first product at an appropriate time point. The above-mentioned addition of titanium and antimony sources can more effectively suppress the rapid consumption of Ti / Sb elements in the early stage of the reaction, making the formation of the coating layer more uniform, thereby more effectively stabilizing the structure of the obtained precursor material and the subsequently obtained cathode material, reducing phase transitions during charging and discharging, and improving its stability to air, water, and carbon dioxide.

[0026] To better control the coprecipitation reaction rate and improve the compositional uniformity of the obtained precursor, the preferred flow rate of solution A is 1.0 L / h to 3.0 L / h, and the preferred flow rate of solution B is 0.5 L / h to 1.5 L / h.

[0027] To more effectively regulate the growth rate and uniformity of the first product, thereby further improving the structural stability of the obtained precursor material, the total molar concentration of metal ions in solution A is preferably 1.0 mol / L to 1.5 mol / L. Furthermore, to better control the formation rate and thickness of the coating layer, and more effectively suppress the influence of an excessively thick coating layer on the diffusion rate of sodium ions, thereby maintaining the structural stability of the material while further improving the electrochemical performance of the obtained precursor material and the subsequent cathode material, the total molar concentration of metal ions in solution B is preferably 0.4 mol / L to 0.6 mol / L.

[0028] Regarding the complexing agent and precipitant used in the above preparation method, in order to promote a more efficient co-precipitation reaction and further improve the purity and structural stability of the obtained precursor material and the subsequently obtained cathode material, it is preferred that: the molar concentration of the complexing agent in the complexing agent solution is 3.5 mol / L to 4.5 mol / L; and / or, the molar concentration of the precipitant in the precipitant solution is 4.5 mol / L to 5.5 mol / L. Furthermore, in practical applications, the complexing agent is selected from one or more of ammonia, ammonium sulfate, ammonium chloride, and citric acid, more preferably ammonia; the precipitant is selected from one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate, more preferably sodium hydroxide.

[0029] Further, in order to more effectively control the uniformity of the reaction, reduce local overheating or uneven reaction phenomena, and thus more significantly optimize the morphology and electrochemical properties of the obtained precursor material, it is preferred that: both step S1 and step S2 are carried out under stirring conditions, and the stirring speed is 400 rpm to 500 rpm; and / or, step S1 and step S2 are each independently carried out at 55°C to 65°C. Also, it is preferred that both step S1 and step S2 are carried out in a protective atmosphere, and the protective atmosphere is nitrogen and / or argon, so as to reduce the occurrence of side reactions and further improve the purity of the prepared precursor material and the electrochemical properties of the finally obtained cathode material.

[0030] In several typical embodiments, the nickel source, iron source, manganese source, titanium source, and antimony source are each independently added in the form of acetate, sulfate, nitrate, and chloride. In several more typical embodiments, the nickel source is selected from one or more of nickel acetate, nickel sulfate, nickel chloride, and nickel nitrate; and / or, the iron source is selected from one or more of iron sulfate, iron chloride, iron nitrate, ferrous sulfate, ferrous chloride, ferrous nitrate, and ferrous acetate; and / or, the manganese source is selected from one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; and / or, the titanium source is titanium sulfate and / or titanium chloride; and / or, the antimony source is antimony chloride and / or antimony nitrate.

[0031] In practical applications, before obtaining the cathode material precursor product, the above preparation method further includes the steps of aging, washing, drying, mixing, sieving, and demagnetizing the product obtained from the second precipitation reaction.

[0032] The second aspect of the present invention provides a cathode material precursor, which is prepared by the above preparation method of the cathode material precursor, and the chemical formula of the cathode material precursor is Ni 0.5-x Fe 0.2 Mn 0.3-y Ti x Sb y (OH)2, where 0.01 < x < 0.1 and 0.005 < y < 0.05. For the precursor prepared by the above preparation method, the elements Ni, Fe, Mn, Ti, and Sb can achieve a more uniform distribution, forming a hydroxide with a stable structure and superior performance. In terms of elemental composition, for the above cathode material precursor prepared by the present invention, doping with the Ti element increases the interplanar spacing of the material, reduces the binding force of the metal oxide layer during the sodium ion extraction / insertion process, and can greatly improve the reversible specific capacity of the battery. However, the increase in the layer spacing also leads to the instability of the overall structure; at the same time, the introduced doping element Sb can form s-2p hybrid orbitals with the 2p orbit of O, enhancing the binding energy between metal ions and oxygen. Finally, it can exhibit higher electrochemical performance and cycle stability after obtaining the cathode material.

[0033] It should be noted that due to the complex structural formation and compositional changes during the preparation process, and the limitations of the material field and existing testing and characterization methods, it is difficult to perform a comprehensive quantitative characterization of the complex microstructure of the obtained cathode material precursor and the arrangement of elements in its crystal structure. However, performance test results show that the cathode material precursor containing the Ti / Sb co-coating layer obtained in this invention exhibits particularly superior electrochemical activity and cycle stability after sintering to obtain the cathode material.

[0034] Furthermore, in order to significantly improve cycle stability and form a more uniform internal structure during the subsequent sintering process to obtain the cathode material, thereby further improving the cycle stability and rate performance of the obtained cathode material, the D50 of the obtained cathode material precursor is preferably 5μm~7μm.

[0035] In several preferred embodiments, the chemical formula of the cathode material precursor is Ni. 0.44 Fe 0.2 Mn 0.27 Ti 0.06 Sb 0.03 (OH)2 or Ni 0.48 Fe 0.2 Mn 0.2 Ti 0.02 Sb 0.01 O2. The cathode material precursor with the above chemical formula can better combine with sodium, thereby further improving the diffusion path of sodium ions in the material after sintering to obtain the cathode material, reducing phase transitions during the electrochemical reaction process, and ultimately significantly improving the cycle stability and rate performance of the subsequently obtained cathode material.

[0036] A third aspect of the present invention provides a cathode material obtained by sequentially mixing and sintering the aforementioned cathode material precursor with a sodium source; the cathode material has the chemical formula NaNi. 0.5-x Fe 0.2 Mn 0.3-y Ti x Sb y O2, where x and y have the same definitions as above. Because the precursor obtained by this invention possesses higher structural stability, better electronic structure, and more suitable elemental composition and distribution, after being mixed and sintered with a sodium source to obtain the cathode material, the corresponding cathode material exhibits smaller structural changes and longer cycle life during battery cycling. It also makes the battery voltage platform more stable and the output power higher. Through extensive experiments, the inventors obtained a cathode material with the chemical formula NaNi in several preferred embodiments. 0.44 Fe 0.2 Mn0.27 Ti 0.06 Sb 0.03 O2 or NaNi 0.48 Fe 0.2 Mn 0.2 Ti 0.02 Sb 0.01 O2, thereby achieving superior electrochemical performance and longer cycle life.

[0037] Furthermore, and more preferably, the cathode material precursor and sodium source are mixed at a molar ratio of 1:(1.0~1.5) and sintered at 700℃~1000℃ to obtain the cathode material. Based on this, the Ti / Sb co-coated cathode material precursor can be transformed into a cathode material with a more stable crystal structure during sintering. Specifically, the sintering temperature of 700℃~1000℃ (more preferably 800±50℃) can effectively optimize the grain growth and phase transformation process of the cathode material. The optimized molar ratio can promote more complete penetration of the sodium source, reduce the sodium ion depletion phenomenon that may occur on the surface of the obtained cathode material, and thus further improve the electrochemical performance.

[0038] In order to more effectively reduce the thermal stress damage of the cathode material during the sintering process and promote its higher cycle stability and energy density, the sintering time is preferably 10h to 20h, the heating rate is 1℃ / min to 5℃ / min (more preferably 2±0.5℃ / min), and the cooling rate is 2℃ / min to 3℃ / min.

[0039] Furthermore, in practical applications, the sodium source is selected from one or more of sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate, sodium oxide, and sodium peroxide.

[0040] A fourth aspect of the present invention provides a positive electrode sheet comprising the aforementioned positive electrode material. By using the positive electrode material with high cycle stability obtained above, the corresponding positive electrode sheet can maintain low voltage polarization and high energy conversion efficiency during battery charging and discharging. Furthermore, the positive electrode material obtained by the present invention possesses high uniformity and stability, thereby significantly reducing side reactions within the electrode sheet and extending its cycle life.

[0041] A fifth aspect of the present invention provides a sodium-ion battery comprising the aforementioned positive electrode. Because the positive electrode material in this electrode possesses excellent electrochemical performance and structural stability, and is not prone to phase transition during use, the resulting battery can maintain stable electrical performance and a long cycle life during high voltage output and high current density charge / discharge processes.

[0042] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0043] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0044] Example 1

[0045] A method for preparing a cathode material precursor:

[0046] (1-1) According to the molecular formula of layered sodium ion cathode material NaNi 0.44 Fe 0.2 Mn 0.27 Ti 0.06 Sb 0.03 O2 (with x=0.06, y=0.03) yielded a molar ratio of Ni:Fe:Mn=0.44:0.2:0.27 (which is converted to 0.488:0.222:0.300). Nickel sulfate, ferrous sulfate, and manganese sulfate were weighed and dissolved in deionized water to prepare a mixed solution A with a total metal ion concentration of 1.2 mol / L.

[0047] (1-2) The mixed solution A from step (1-1), 4 mol / L complexing agent ammonia solution and 5 mol / L precipitant sodium hydroxide solution are added to the reaction vessel by a metering pump at a flow ratio of 1:0.9:0.9 (where the flow rate of mixed solution A is 1.5 L / h). The pH in the reaction vessel is maintained at 10.80, the reaction temperature is 60℃, and the stirring speed of the reaction vessel is 450 rpm.

[0048] (2-1) Prepare a Ti / Sb mixed solution B by mixing titanium sulfate and antimony chloride in a Ti / Sb molar ratio of 2:1, wherein the total metal ion concentration is 0.5 mol / L.

[0049] (2-2) When the crystal particles D50 in the coprecipitation reaction in step (1-2) grow to 4µm, solution B is introduced at the same time as solution A to continue the coating coprecipitation reaction. The flow rate ratio of solution B, ammonia solution and sodium hydroxide solution is 1:0.9:0.9 (where the flow rate of mixed solution B is 0.8L / h); the process is stopped when the reactant particles D50 grow to 6µm.

[0050] (3) The slurry after the reaction is completed is aged, washed, dried, mixed, sieved, and demagnetized to obtain the Ti / Sb co-coated precursor material Ni. 0.44 Fe 0.2 Mn 0.27Ti 0.06 Sb 0.03 (OH)2.

[0051] The obtained cathode material precursor Ni 0.44 Fe 0.2 Mn 0.27 Ti 0.06 Sb 0.03 The SEM characterization results of (OH)2 are shown in [the table below]. Figure 1 .

[0052] A method for preparing a cathode material: Sodium carbonate and the aforementioned precursor material are ball-milled at a molar ratio of 1.02:1 for 6 hours at a speed of 500 rpm. Subsequently, the mixed material is sintered in a tube furnace at a temperature of 800℃, a heating rate of 2℃ / min, and a sintering time of 16 hours. After sintering, the cooling rate is 3℃ / min, yielding the cathode material for sodium-ion batteries with the chemical formula NaNi. 0.44 Fe 0.2 Mn 0.27 Ti 0.06 Sb 0.03 O2.

[0053] The obtained cathode material NaNi 0.44 Fe 0.2 Mn 0.27 Ti 0.06 Sb 0.03 The SEM characterization results of O2 are shown below. Figure 2 .

[0054] Example 2

[0055] A method for preparing a cathode material precursor:

[0056] The only difference between this embodiment and Embodiment 1 is that the molar ratio of each raw material is changed, and the final product with the chemical formula Ni is obtained. 0.48 Fe 0.2 Mn 0.29 Ti 0.02 Sb 0.01 O2 (x=0.02, y=0.01) cathode material precursor.

[0057] A method for preparing a cathode material:

[0058] Consistent with Example 1, and ultimately yielding the chemical formula NaNi 0.48 Fe 0.2 Mn 0.2 Ti 0.02 Sb 0.01 O2 cathode material.

[0059] Example 3

[0060] A method for preparing a cathode material precursor:

[0061] The only difference between this embodiment and Embodiment 1 is that, in step (1-1), the total molar concentration of metal ions in solution A is changed to 0.8 mol / L.

[0062] A method for preparing a positive electrode material: consistent with Example 1.

[0063] Example 4

[0064] A method for preparing a cathode material precursor:

[0065] The only difference between this embodiment and Embodiment 1 is that, in step (1-1), the total molar concentration of metal ions in solution A is changed to 1.8 mol / L.

[0066] A method for preparing a positive electrode material: consistent with Example 1.

[0067] Example 5

[0068] A method for preparing a cathode material precursor:

[0069] The only difference between this embodiment and Embodiment 1 is that in step (1-2), the flow ratio of solution A, complexing agent ammonia solution and precipitant sodium hydroxide solution is changed to 1:1:1, and the reaction is changed to be carried out under the condition of pH=12.

[0070] A method for preparing a positive electrode material: consistent with Example 1.

[0071] Example 6

[0072] A method for preparing a cathode material precursor:

[0073] The only difference between this embodiment and Example 1 is that in step (1-2), the flow ratio of solution A, complexing agent ammonia solution and precipitant sodium hydroxide solution is changed to 1:0.8:0.8, and the reaction is changed to be carried out under the condition of pH=10.

[0074] A method for preparing a positive electrode material: consistent with Example 1.

[0075] Example 7

[0076] A method for preparing a cathode material precursor:

[0077] The only difference between this embodiment and Embodiment 1 is that, in step (2-1), the total molar concentration of metal ions in solution B is changed to 0.8 mol / L.

[0078] A method for preparing a positive electrode material: consistent with Example 1.

[0079] Example 8

[0080] A method for preparing a cathode material precursor:

[0081] The only difference between this embodiment and Embodiment 1 is that, in step (2-1), the total molar concentration of metal ions in solution B is changed to 0.2 mol / L.

[0082] A method for preparing a positive electrode material: consistent with Example 1.

[0083] Example 9

[0084] A method for preparing a cathode material precursor:

[0085] The only difference between this embodiment and Example 1 is that the molar concentration of the complexing agent ammonia solution is changed to 5 mol / L, and the molar concentration of the precipitant sodium hydroxide solution is changed to 4 mol / L.

[0086] A method for preparing a positive electrode material: consistent with Example 1.

[0087] Example 10

[0088] A method for preparing a cathode material precursor:

[0089] The only difference between this embodiment and Example 1 is that the molar concentration of the complexing agent ammonia solution is changed to 3 mol / L, and the molar concentration of the precipitant sodium hydroxide solution is changed to 6 mol / L.

[0090] A method for preparing a positive electrode material: consistent with Example 1.

[0091] Example 11

[0092] A method for preparing a cathode material precursor:

[0093] The only difference between this embodiment and Embodiment 1 is that the temperature of the reactor is changed to 50°C and the stirring speed is changed to 350 rpm.

[0094] A method for preparing a positive electrode material: consistent with Example 1.

[0095] Example 12

[0096] A method for preparing a cathode material precursor:

[0097] The only difference between this embodiment and Embodiment 1 is that the temperature of the reactor is changed to 60°C and the stirring speed is changed to 550 rpm.

[0098] A method for preparing a positive electrode material: consistent with Example 1.

[0099] Example 13

[0100] A method for preparing a cathode material precursor: consistent with Example 1.

[0101] A method for preparing a cathode material:

[0102] The only difference between this embodiment and Embodiment 1 is that the heating rate during the sintering process is changed to 1℃ / min, the sintering temperature is changed to 700℃, the sintering time is changed to 20h, and the cooling rate after sintering is changed to 4℃ / min.

[0103] Example 14

[0104] A method for preparing a cathode material precursor: consistent with Example 1.

[0105] A method for preparing a cathode material:

[0106] The only difference between this embodiment and Embodiment 1 is that the heating rate during the sintering process is changed to 5℃ / min, the sintering temperature is changed to 1000℃, the sintering time is changed to 10h, and the cooling rate after sintering is changed to 1℃ / min.

[0107] Comparative Example 1

[0108] A method for preparing a cathode material precursor:

[0109] The difference between this comparative example and Example 1 lies only in step (2-2). Specifically, when the crystal particle size D50 in the co-precipitation reaction of step (1-2) grows to 3µm, solution B is introduced simultaneously with solution A to continue the coating co-precipitation reaction. The flow rate ratio of solution B, ammonia solution, and sodium hydroxide solution is controlled to be consistent with that in Example 1; the process is stopped when the reactant particle size D50 grows to 6µm.

[0110] A method for preparing a positive electrode material: consistent with Example 1.

[0111] Comparative Example 2

[0112] A method for preparing a cathode material precursor:

[0113] The difference between this comparative example and Example 1 lies only in step (2-2). Specifically, when the crystal particle size D50 in the co-precipitation reaction of step (1-2) grows to 6µm, solution B is introduced simultaneously with solution A to continue the coating co-precipitation reaction. The flow rate ratio of solution B, ammonia solution, and sodium hydroxide solution is controlled to be consistent with that in Example 1; the process is stopped when the reactant particle size D50 grows to 6µm.

[0114] A method for preparing a positive electrode material: consistent with Example 1.

[0115] Comparative Example 3

[0116] A method for preparing a cathode material precursor:

[0117] The only difference between this comparative example and Example 1 is that in step (2-1), the molar ratio of the titanium source to the antimony source is changed to 1:1.

[0118] A method for preparing a positive electrode material: consistent with Example 1.

[0119] Comparative Example 4

[0120] A method for preparing a cathode material precursor:

[0121] The only difference between this comparative example and Example 1 is that in step (2-1), the molar ratio of titanium source to antimony source is changed to 3:1.

[0122] A method for preparing a positive electrode material: consistent with Example 1.

[0123] Comparative Example 5

[0124] A method for preparing a cathode material precursor:

[0125] The only difference between this comparative example and Example 1 is that steps (1-2) and (2-2) were not performed. Instead, the mixed solution A, mixed solution B, ammonia solution, and sodium hydroxide solution prepared in Example 1 were all introduced into the reactor at a flow ratio of 1:1:0.9:0.9 and reacted to obtain reactant particles with a D50 of 6µm. After aging, washing, drying, mixing, sieving, and demagnetizing, the cathode material precursor was obtained.

[0126] A method for preparing a positive electrode material: consistent with Example 1.

[0127] Battery Sample Preparation and Testing Methods

[0128] The sodium-ion cathode materials provided in the above examples and comparative examples were mixed with SP and PVDF at a mass ratio of 94:3:3. After uniform mixing, N-methylpyrrolidone was added, and the mixture was stirred at 1500 rpm for 15 minutes using a homogenizer. After forming a uniform slurry, it was coated onto aluminum foil with an 80 μm doctor blade and then vacuum-baked at 85°C. The dried electrode was then rolled and finally cut into cathode sheets with a diameter of 14 mm, wherein the areal density of the electrode sheet was 10.8 mg / cm³. 2 Electrode compaction 3.0 g / cm 3A sodium-ion battery was assembled using a 16mm diameter pure sodium sheet as the negative electrode, ENA 18 electrolyte (Guangzhou Tinci Advanced Materials Co., Ltd.), and a GF / D glass fiber separator in an argon-filled glove box.

[0129] At 25°C and within a voltage range of 2V to 4V, the 0.1C discharge specific capacity, 1C discharge specific capacity, 3C rate discharge capacity retention rate under a 0.1C charge / 3C discharge regime, and capacity retention rate after 100 cycles at 1C were tested for the sodium-ion cathode materials provided in all the above embodiments and comparative examples.

[0130] The cathode materials obtained from each embodiment and comparative example were used to prepare corresponding battery samples in the manner described above. The performance of each sample was then tested in the manner described above, and the results are shown in Table 1.

[0131] Table 1

[0132]

[0133] As can be seen from the above description, the embodiments of the present invention, by optimizing the preparation method of the precursor, enhance the stability of the obtained precursor material and the subsequent obtained cathode material against air and the ability to resist H2O and CO2 corrosion. While improving the electrochemical activity of the precursor material, the structural stability of the subsequently obtained cathode material during the charge and discharge process is also improved, thereby ensuring the long cycle performance and high power characteristics of the final battery.

[0134] Specifically, this invention introduces high bond energy elements Ti and Sb into the outer core of sodium nickel iron manganese oxide. By controlling the size of the core and shell, as well as the proportion of Ti and Sb in the entire material, the interlayer spacing and lattice distortion of the cathode material are controlled, thereby improving the structural stability of the material and enhancing the diffusion efficiency of Na ions, thus achieving a simultaneous improvement in cycle performance and rate performance.

[0135] In various embodiments:

[0136] Comparing Examples 3 and 4 with Example 1, it can be seen that by optimizing the total molar concentration of metal ions in solution A, the growth rate and uniformity of the first product can be more effectively controlled, thereby further improving the structural stability of the obtained precursor material and ultimately enhancing the electrochemical performance and cycle stability of the final cathode material.

[0137] Comparing Examples 5 and 6 with Example 1, it can be seen that by optimizing the flow ratio of solution A, complexing agent, and precipitant, and optimizing the pH conditions for the first precipitation reaction of the three, the effective reaction between metal ions and complexing agent can be promoted, forming a more uniform complex state of metal ions, which is more conducive to subsequent uniform precipitation and reduces the chemical heterogeneity inside the obtained precursor material. At the same time, the precipitation of metal hydroxide is further optimized, reducing the formation of excessive hydroxide by-products, thereby significantly improving the purity and crystal quality of the precipitate, and finally preparing a cathode material precursor with superior performance, which significantly improves the performance of the subsequently obtained cathode material.

[0138] Comparing Examples 9 and 10 with Example 1, it can be seen that by further optimizing the molar concentrations of the complexing agent solution and the precipitant solution, the co-precipitation reaction can be promoted to proceed more efficiently, while further improving the purity and structural stability of the obtained precursor material and the subsequently obtained cathode material.

[0139] Comparing Examples 7 and 8 with Example 1, it can be seen that by optimizing the total molar concentration of metal ions in solution B, the formation rate and thickness of the coating layer can be better controlled, and the effect of an excessively thick coating layer on the diffusion rate of sodium ions can be more effectively suppressed. Thus, while maintaining the stability of the material structure, the electrochemical performance of the obtained precursor material and the subsequent cathode material can be further improved.

[0140] Comparing Examples 11 and 12 with Example 1, it can be seen that by optimizing the temperature and stirring conditions of the reactor, i.e., optimizing the conditions of the second precipitation reaction, the uniformity of the reaction can be controlled more effectively, reducing local overheating or uneven reaction phenomena, thereby significantly optimizing the morphology and electrochemical performance of the obtained precursor material.

[0141] Comparing Examples 13 and 14 with Example 1, it can be seen that by optimizing the sintering conditions, the grain growth and phase transformation process of the cathode material can be well optimized, and the thermal stress damage of the cathode material during the sintering process can be reduced more effectively, thus promoting its higher cycle stability and energy density.

[0142] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0143] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a cathode material precursor, characterized in that, include: In step S1, solution A, complexing agent, and precipitant undergo a first precipitation reaction in a reaction vessel to obtain a first product with a D50 of 3.5 μm to 4.5 μm; Step S2: Add solution B to the reaction vessel and obtain the cathode material precursor through a second precipitation reaction; Solution A includes a nickel source, an iron source, and a manganese source, and the molar ratio of the nickel source, the iron source, and the manganese source is (0.45~0.50):(0.20~0.25):(0.28~0.32). The solution B includes a titanium source and an antimony source, and the molar ratio of the titanium source to the antimony source is (1.5~2.5):

1.

2. The method for preparing the cathode material precursor according to claim 1, characterized in that, include: Step S1-1: Prepare the nickel source, the iron source and the manganese source into solution A, prepare the complexing agent into a complexing agent solution, and prepare the precipitant into a precipitant solution; In step S1-2, the solution A, the complexing agent solution, and the precipitant solution are fed into the reaction vessel, and the first precipitation reaction is carried out under the condition of pH 10.5~11.5 to obtain a reaction solution containing the first product. Step S2-1: Prepare solution B by mixing the titanium source and the antimony source; In step S2-2, under the condition that the solution A, the complexing agent solution and the precipitant solution are kept flowing in, the solution B is flowed into the reaction vessel containing the reaction solution, and the positive electrode material precursor is obtained through the second precipitation reaction.

3. The method for preparing the cathode material precursor according to claim 2, characterized in that, The flow rate ratio of solution A, the complexing agent solution, and the precipitant solution is 1:(0.85~0.95):(0.85~0.95). The flow rate ratio of solution B, the complexing agent solution, and the precipitant solution is 1:(0.85~0.95):(0.85~0.95). The flow rate of solution A is 1.0 L / h to 3.0 L / h, and the flow rate of solution B is 0.5 L / h to 1.5 L / h.

4. The method for preparing the cathode material precursor according to claim 3, characterized in that, In solution A, the total molar concentration of metal ions is 1.0 mol / L to 1.5 mol / L; and / or, In solution B, the total molar concentration of metal ions is 0.4 mol / L to 0.6 mol / L; and / or, In the complexing agent solution, the molar concentration of the complexing agent is 3.5 mol / L to 4.5 mol / L; and / or, In the precipitant solution, the molar concentration of the precipitant is 4.5 mol / L to 5.5 mol / L; Preferably, the complexing agent is selected from one or more of ammonia, ammonium sulfate, ammonium chloride, and citric acid, more preferably ammonia; the precipitant is selected from one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate, more preferably sodium hydroxide.

5. The method for preparing the cathode material precursor according to any one of claims 1 to 4, characterized in that, Both steps S1 and S2 are performed under stirring conditions, and the stirring speed is 400 rpm to 500 rpm; and / or, Step S1 and step S2 are each performed independently at 55°C to 65°C; and / or, Both steps S1 and S2 are performed in a protective atmosphere, which is nitrogen and / or argon.

6. The method for preparing the cathode material precursor according to any one of claims 1 to 5, characterized in that, The nickel source, the iron source, the manganese source, the titanium source, and the antimony source are each added independently in the form of acetate, sulfate, nitrate, and chloride. Preferably, the nickel source is selected from one or more of nickel acetate, nickel sulfate, nickel chloride, and nickel nitrate; and / or, the iron source is selected from one or more of ferric sulfate, ferric chloride, ferric nitrate, ferrous sulfate, ferrous chloride, ferrous nitrate, and ferrous acetate; and / or, the manganese source is selected from one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; and / or, the titanium source is titanium sulfate and / or titanium chloride; and / or, the antimony source is antimony chloride and / or antimony nitrate.

7. A cathode material precursor, characterized in that, The cathode material precursor is prepared by the method for preparing the cathode material precursor according to any one of claims 1 to 6, and the chemical formula of the cathode material precursor is Ni. 0.5- x Fe 0.2 Mn 0.3-y Ti x Sb y (OH)2, of which 0.01 <x<0.1,0.005<y<0.05; Preferably, the D50 of the cathode material precursor is 5μm~7μm.

8. A positive electrode material, characterized in that, The cathode material is obtained by sequentially mixing and sintering the cathode material precursor as described in claim 7 with a sodium source; the chemical formula of the cathode material is NaNi. 0.5-x Fe 0.2 Mn 0.3-y Ti x Sb y O2, where x and y have the same definitions as described in claim 7.

9. A positive electrode sheet, characterized in that, The positive electrode sheet includes the positive electrode material as described in claim 8.

10. A sodium-ion battery, characterized in that, The sodium-ion battery includes the positive electrode sheet as described in claim 9.

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