A sodium-ion battery positive electrode material and a preparation method and application thereof

Abstract

This invention belongs to the field of sodium-ion battery technology, and relates to a sodium-ion battery cathode material, its preparation method, and its application. The general chemical formula of the sodium-ion battery cathode material in this invention is Na(Ni) 0.3 Fe 0.3 Mn 0.3 Cu x Ti 0.1‑x )O 2‑y F y Where x = 0.04~0.06, y = 0.04~0.05, this material uses Ni as the sodium-ion battery cathode precursor. 1 / 3 Fe 1 / 3 Mn 1 / 3 Using (OH)2, sodium source, and additives containing copper / titanium / fluorine sources as raw materials, the raw materials are mixed and sintered to obtain sintered material. After cooling, the sintered material is coarsely crushed, pulverized, sieved, and demagnetized to prepare the final product. This invention improves the cycle performance of the material by doping with oxygen-negative elements (fluorine) that increase structural stability, and by doping with metallic elements (copper, titanium) to mitigate oxidative degradation, thereby reducing the adverse effects of air sensitivity. The ternary synergistic doping of Cu+Ti+F in the material achieves complementary advantages and synergistic performance, thus endowing the material with excellent comprehensive performance. When this material is applied to sodium-ion batteries, it can significantly improve the electrical performance of sodium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and relates to a sodium-ion battery cathode material, its preparation method and application. Background Technology

[0002] Sodium-ion batteries have become a popular product due to their low production cost and the availability of sodium. Sodium-ion battery cathode materials do not rely on expensive cobalt, but instead use lower-cost iron and copper, thus exhibiting a greater cost advantage. Currently, many manufacturers of sodium-ion battery cathode materials have applied them to EV products and received positive feedback.

[0003] Sodium-ion battery cathode materials are classified into transition metal oxides, polyanionic compounds, and PB cathode materials. Among these types, layered transition oxide cathode materials exhibit higher theoretical specific capacity and their production methods largely overlap with the current large-scale production lines for ternary materials, thus attracting considerable research attention. Currently, publicly disclosed types of layered oxides include sodium copper-iron-manganese oxide from Zhongke Haina, sodium iron-nickel-manganese oxide from Sodium Innovation Energy, and manganese-iron-cyanide cathode materials from Cubic New Energy, among others.

[0004] Currently, the process for preparing layered oxides for sodium-ion batteries is the co-precipitation-high-temperature solid-state method, which involves preparing a precursor through co-precipitation and then sintering the precursor at high temperature to obtain the cathode material.

[0005] Coprecipitation can achieve atomic-level mixing through reactions within the solution. This involves adding complexing and precipitating agents to the raw material solution, causing the already uniformly mixed ions to precipitate together in stoichiometric proportions. After filtration and drying, the desired precursor can be obtained. For example, patent document CN115974174A discloses a method for preparing a precursor of sodium-ion battery cathode material, including the following steps: preparing a metal salt solution (nickel salt, iron salt, manganese salt), a precipitant solution (sodium hydroxide), and a complexing agent solution (ammonia); adding a reducing agent (citric acid, sodium citrate, or oxalic acid) to the metal salt solution to obtain a mixed solution, wherein the concentration of the reducing agent in the mixed solution is 1~10 g / L; adding water, the complexing agent solution, and the precipitant solution to a reaction vessel to prepare a bottom liquid for the reaction vessel; adding the mixed solution to the reaction vessel to carry out a co-precipitation reaction (temperature 50~70℃, pH value 10~12), reacting until the particle size grows to the target particle size (D50 value 3~6 μm), stopping the feeding, and obtaining a solution containing precursor material; stirring the precursor material solution for aging, washing, drying, sieving, and iron removal to obtain the precursor of sodium-ion battery cathode material.

[0006] The coprecipitation-high-temperature solid-state method first obtains a precursor through coprecipitation, and then obtains the final product through calcination decomposition and crystallization. The advantage of the coprecipitation method is that the particle size and morphology of the prepared precursor can be controlled, particle uniformity can be effectively guaranteed, and atomic-level mixing can be achieved. The coprecipitation-high-temperature solid-state method involves mixing the precursor synthesized in the previous coprecipitation method with a sodium salt and then sintering it at high temperature. For example, patent document CN117154074A discloses a method for preparing sodium-ion battery cathode material, including the following steps: adding deionized water to a reaction vessel, then adding ammonia, chelating agent solution and sodium hydroxide solution in sequence, controlling the pH to 10.3~12.5, and controlling the reaction temperature to 40~70℃±1℃; adding raw materials to the reaction vessel for co-precipitation reaction, controlling the pH to 10.3~11.6, maintaining for 40~90h, then transferring the solution to a centrifuge for solid-liquid separation to obtain wet precursor material, drying the wet material at 110~120℃ for 10~20h to obtain sodium-ion cathode material precursor product; mixing the precursor product with Na2CO3 and placing it in a box furnace for solid-phase sintering at 850~970℃ for 7~15h, then coarsely crushing, finely crushing and sieving to obtain sodium-ion battery cathode material.

[0007] However, the cathode materials prepared using the aforementioned existing technologies have the following drawbacks: First, irreversible phase transition: The irreversible phase transition of layered transition metal oxides under high temperature and pressure is a significant issue during charge-discharge cycling. During electrochemical cycling, both the P2 and O3 phases undergo a series of phase transitions. This occurs during the insertion and extraction of sodium ions in the layered structure under high temperature and pressure, irreversibly leading to changes in the volume of the layered structure and slippage of the transition metal oxide layer. Ultimately, this results in structural phase transitions, even collapse, and rapid capacity decay. Second, air instability: Sodium-ion layered oxide cathode materials are prone to deliquescence and are highly sensitive to air. Sample materials may experience volume expansion or even cracking. Water molecules are not only adsorbed on the material surface but also inserted into the transition metal oxide layer, hindering the migration of sodium ions. Furthermore, the presence of carbon dioxide in the air leads to the formation of sodium carbonate and sodium hydroxide on the surface of the sodium-ion layered oxide cathode material, which will result in a decrease in capacity. Summary of the Invention

[0008] Based on this, the purpose of this invention is to provide a sodium-ion battery cathode material, which is a layered sodium-ion cathode material with disordered sodium ion vacancy arrangement and co-doped with cations (Cu, Ti) and anions (F). The ternary co-doping of Cu + Ti + F in the material achieves complementary advantages and synergistic performance, thereby endowing the material with excellent comprehensive performance.

[0009] This invention also provides a method for preparing a sodium-ion battery cathode material. This method mainly adopts a high-temperature solid-state method, which has a simple process flow, readily available raw materials, and is easy to scale up for production.

[0010] The present invention also provides an application of a sodium-ion battery cathode material in sodium-ion batteries. By using this material as an active material in the cathode sheet of sodium-ion batteries, the electrical performance of sodium batteries can be effectively improved.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] This invention provides a sodium-ion battery cathode material, wherein the general chemical formula of the sodium-ion battery cathode material is Na(Ni) 0.3 Fe 0.3 Mn 0.3 Cu x Ti 0.1-x )O 2-y F y , where x = 0.04~0.06, y = 0.04~0.05.

[0013] This invention further provides a method for preparing a sodium-ion battery cathode material, using a sodium-ion battery cathode precursor, a sodium source, and additives as raw materials. The raw materials are mixed and then sintered to obtain a sintered material. After cooling, the sintered material is coarsely crushed, pulverized, sieved, and demagnetized to obtain the sodium-ion battery cathode material. The sodium-ion battery cathode precursor is Ni. 1 / 3 Fe 1 / 3Mn 1 / 3 (OH)2, wherein the additives include copper source, titanium source and fluorine source.

[0014] Further, the sodium source includes sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium nitrate, or sodium sulfate; the copper source includes copper sulfate, copper chloride, or copper oxide; the titanium source includes titanium dioxide, titanium tetrachloride, or titanium trichloride; and the fluorine source includes sodium fluoride.

[0015] Furthermore, the purity of the sodium source is greater than 98%, and the purity of the sodium carbonate, sodium bicarbonate, and sodium hydroxide is battery grade or industrial grade; the purity of the copper source, titanium source, and fluorine source is greater than 99%.

[0016] Furthermore, the molar ratio of the sum of nickel, iron, and manganese, sodium source, copper source, titanium source, and fluorine source in the sodium-ion cathode precursor is 1: 1.01~1.08: 0.02~0.08: 0.02~0.08: 0.02~0.08.

[0017] Furthermore, the sintering temperature is 950~1000℃, the sintering time is 10~15h, and the heating rate is 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min.

[0018] Furthermore, the sintered material is subjected to coarse crushing after being naturally cooled to 70~100℃, and the sieve used for screening has a mesh size of 200~400 mesh.

[0019] Furthermore, the raw materials are mixed using a star ball mill, a high-speed mixer, or a plow mill, with a mixing frequency of 50±5Hz and a mixing time of 20~30 minutes; the sintered materials are coarsely crushed using a jaw crusher, a single-layer roller mill, or a double-layer roller mill, then pulverized using a grinder, an air jet mill, or a mechanical pulverizer, and finally sieved through a 200~400 mesh screen.

[0020] Furthermore, the raw materials are mixed and then placed into a sagger, and sintered using a box-type atmosphere furnace; the sagger is made of corundum or mullite; the sintering atmosphere is a mixture of nitrogen and oxygen.

[0021] Furthermore, the median particle size D50 of the sodium-ion cathode precursor is 4~15μm; it is prepared by first adding nickel source, manganese source and iron source in a molar ratio of 1:1:1 to the bottom liquid for co-precipitation reaction, aging to obtain a reaction solution containing nickel manganese iron hydroxide, then performing solid-liquid separation on the reaction solution to obtain crude nickel manganese iron hydroxide, and then preparing the crude nickel manganese iron hydroxide by alkaline washing, water washing and drying.

[0022] Further, the nickel source includes at least one of nickel sulfate, nitrate, and chloride; the manganese source includes at least one of manganese sulfate, nitrate, and chloride; the iron source includes at least one of iron sulfate, nitrate, and chloride; the bottom solution consists of a complexing agent aqueous solution with a concentration of 0.2~2.5 mol / L and a precipitant aqueous solution with a concentration of 5~20 mol / L, wherein the complexing agent includes at least one of ammonia, sodium citrate, disodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate; and the precipitant includes sodium hydroxide or sodium carbonate.

[0023] Furthermore, during the coprecipitation reaction, the pH of the underlying solution is 10-11.8, the temperature is 45-65℃, and the stirring rate is 00-1500 r / min.

[0024] Furthermore, the endpoint of the alkaline washing is when the conductivity of the washing liquid is <500 μs / cm, and the endpoint of the water washing is when the conductivity of the washing liquid is <60 μs / cm.

[0025] Furthermore, the drying temperature is 100~200℃, the time is 12~20h, preferably a static dryer is used for drying, more preferably a disc dryer is used for drying, and the drying endpoint is that the moisture content of the material is <1000ppm.

[0026] The present invention further provides an application of the above-mentioned sodium-ion battery cathode material in sodium-ion batteries.

[0027] Furthermore, the sodium-ion battery includes a positive electrode sheet containing an active material, which is the positive electrode material of the sodium-ion battery.

[0028] The beneficial effects of this invention are:

[0029] 1. The method for preparing sodium-ion battery cathode material provided by the present invention improves the cycle performance of sodium-ion battery cathode material by doping with elements with high oxygen negativity (fluorine) that can increase structural stability, and reduces the oxidative degradation of sodium-ion battery cathode material by doping with metal elements (copper, titanium), thereby reducing the adverse effects of its air sensitivity.

[0030] 2. The sodium-ion battery cathode material provided by this invention is a layered sodium-ion cathode material with disordered sodium ion vacancy arrangement, co-doped with cations (Cu, Ti) and anions (F). The ternary co-doping of Cu + Ti + F in the material achieves complementary advantages and synergistic performance, thereby endowing the material with excellent comprehensive performance.

[0031] 3. This invention applies sodium-ion battery cathode materials to sodium-ion batteries, which can significantly improve the electrical performance of sodium-ion batteries and is of great significance for the future development of battery cells. Attached Figure Description

[0032] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Appendix Figure 1 This is a schematic diagram of the preparation process of the sodium-ion battery cathode material in this invention;

[0034] Appendix Figure 2 The above images show SEM test images of the sodium-ion battery cathode materials in Example 1 and Comparative Example 4 of this invention, with a scale bar of 10 μm. In the images, the upper left and upper right are test images of Example 1 at different magnifications, and the lower left and lower right are test images of Comparative Example 4 at different magnifications.

[0035] Appendix Figure 3This is a graph showing the capacity retention rate of sodium-ion batteries containing different sodium-ion battery cathode materials in the embodiments and comparative examples of the present invention under high-rate discharge.

[0036] Appendix Figure 4 This is a graph showing the capacity retention rate of sodium-ion batteries containing different sodium-ion battery cathode materials in the embodiments and comparative examples of the present invention after 100 cycles. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All mentioned embodiments are implemented based on the technical solutions of the present invention, and detailed implementation processes are given. However, it should be stated that the scope of protection of the present invention is not limited to the following embodiments.

[0038] The preparation process of the sodium-ion battery cathode material in this invention is as follows: Figure 1 As shown. The first step of this method is to prepare a sodium-ion battery cathode precursor. First, a solution is prepared (the molar ratio of nickel source, manganese source, and iron source in the solution is 1:1:1). A complexing agent solution and a precipitant solution are prepared first, and the mixture is added to the reaction vessel as the base solution. Then, the nickel source, manganese source, and iron source are added to the base solution in a molar ratio of 1:1:1 for co-precipitation reaction (preferably, the molar ratio of metal salt, complexing agent, and precipitant is 1:0.2:7~9). After aging, a reaction solution containing nickel-manganese-iron hydroxide is obtained (preferably, the aging process is: stirring at 300±10 rpm at 55~65℃ for 11~13 h, keeping the ambient pH constant (pH 10~11.8), and ensuring the entire process is under a nitrogen atmosphere). The reaction solution is then subjected to solid-liquid separation to obtain crude nickel-manganese-iron hydroxide. This crude nickel-manganese-iron hydroxide is then subjected to alkali washing, water washing, and drying to prepare the precursor Ni. 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 (NFM111). The second step of this method is to perform high-temperature solid-state sintering. First, the precursor NFM111 is mixed evenly with ammonium salt and additives, and then sintered to obtain sintered material. After cooling, the sintered material is coarsely crushed, pulverized, sieved and demagnetized to obtain the sodium-ion battery cathode material.

[0039] The following embodiments provide detailed implementation procedures for the technical solutions of the present invention. Unless otherwise specified, the experimental methods used in the following experimental examples are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0040] Example 1

[0041] (1) The preparation of sodium-ion battery cathode materials mainly includes the following steps:

[0042] 0.2 mol / L NH3•H2O and 8 mol / L sodium hydroxide aqueous solution were used as the base solutions, 100 L each, and added to the reactor. The initial pH of the base solutions was 10.5, and the reaction temperature was 50℃. Nickel sulfate hexahydrate, manganese sulfate tetrahydrate, and ferric sulfate nonahydrate were weighed out in a molar ratio of nickel:manganese:iron = 1:1:1 and gradually added to the base solutions under a nitrogen atmosphere to prepare a 0.5 mol / L metal solution. The stirring rate was 1000 r / min, and the reaction endpoint was a D50 of 5 μm. Alkaline washing was then performed using sodium hydroxide aqueous solution as the alkaline washing solvent. The conductivity of the washing solution was less than 500 μS / cm, and the endpoint of water washing was a conductivity of less than 60 μS / cm. Drying was carried out at 150℃ for 18 h using a disc dryer. The drying endpoint was a moisture content of less than 1000 ppm, and the obtained sodium-ionized precursor was Ni. 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2.

[0043] Ni, a sodium-ion precursor 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 is uniformly mixed with sodium source and additives and sintered using a box-type atmosphere furnace. The resulting cathode material has a single crystal morphology. The material blocks are relatively hard and are then pulverized using a jaw crusher and a roller mill. The resulting material is then processed through a vibrating screen. The sodium source was industrial-grade sodium hydroxide. A high-speed mixer was used to mix the precursor and sodium source at 50 Hz for 25 minutes. The molar ratio of nickel, iron, and manganese in the precursor to the sodium source in the sodium-ion cathode material was 1:1.01. The additive had a purity of 99.5%, and its addition ratio was a molar ratio of nickel, iron, and manganese in the precursor to copper sulfate, titanium dioxide, and sodium fluoride = 1:0.05:0.05:0.05. The mixed material was placed in a corundum sagger and sintered at 950°C for 12 hours at a rate of 2°C / min. The sintering atmosphere was a mixture of nitrogen and oxygen. The sintered material was then passed through a jaw crusher and rollers, pulverized using a grinder, and sieved through a 400-mesh vibrating screen. After demagnetization, Na(Ni) was obtained. 0.3 Fe 0.3 Mn 0.3 Cu 0.05 Ti 0.05 )O 1.95 F 0.05 Layered sodium-ion battery cathode material.

[0044] (2) The preparation of sodium-ion batteries mainly includes the following steps:

[0045] The positive electrode active material (Na(Ni) prepared in step (1) is used to obtain the positive electrode active material) 0.3 Fe 0.3 Mn 0.3 Cu0.05 Ti 0.05 )O 1.95 F 0.05 A layered sodium-ion battery positive electrode material, a binder of polyvinylidene fluoride (PVDF), a conductive agent of carbon black (SP), and a conductive agent of carbon nanotubes (CNTs) were uniformly dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 80:10:8:2 to obtain a positive electrode slurry; the negative electrode active material was a sodium metal sheet (purity >99%). The positive electrode slurry was uniformly and stably coated on the surface of aluminum foil, with a positive electrode coating surface density of 120 g / m². 2 After drying, rolling, and slitting, the positive electrode sheet is obtained, with a compacted density of 2.35 g / m³. 3 Then, the electrodes were punched into circular plates with a diameter of 12 mm using a punching machine. Assembly was carried out in an argon-filled glove box (2.5 g of electrolyte was injected, with an electrolyte formulation mass fraction ratio of EC:DMC:NaClO4:VC:PS=23:57:10:5:5). After coin cell activation, a sodium-ion coin cell was obtained.

[0046] Example 2

[0047] The additive was added in a molar ratio, i.e., the sum of nickel, iron, and manganese in the precursor: copper sulfate: titanium dioxide: sodium fluoride = 1:0.05:0.05:0.04. Other experimental procedures were the same as in Example 1. Finally, Na(Ni) was obtained. 0.3 Fe 0.3 Mn 0.3 Cu 0.05 Ti 0.05 )O 1.96 F 0.04 A layered sodium-ion battery cathode material was developed; and a sodium-ion coin cell containing this material was prepared.

[0048] Example 3

[0049] The additive was added in a molar ratio, i.e., the sum of nickel, iron, and manganese in the precursor: copper oxide: titanium dioxide: sodium fluoride = 1:0.04:0.06:0.05. Other experimental procedures were the same as in Example 1. Finally, Na(Ni) was obtained. 0.3 Fe 0.3 Mn 0.3 Cu 0.04 Ti 0.06 )O 1.95 F 0.05 A layered sodium-ion battery cathode material was developed; and a sodium-ion coin cell containing this material was prepared.

[0050] Example 4

[0051] The mixed materials were placed in a corundum sagger and sintered at 980°C at a rate of 2°C / min for 12 hours. Other experimental procedures were the same as in Example 1. Na(Ni) was finally obtained. 0.3 Fe 0.3 Mn0 .3 Cu 0.05 Ti0 .05 )O 1.95 F 0.05 A layered sodium-ion battery cathode material was prepared at -980℃ for 12 hours; and a sodium-ion coin cell containing this material was prepared.

[0052] Example 5

[0053] The mixed materials were placed in a corundum sagger and sintered at 1000°C at a rate of 2°C / min for 12 hours. Other experimental procedures were the same as in Example 1. Na(Ni) was finally obtained. 0.3 Fe 0.3 Mn 0.3 Cu 0.05 Ti 0.05 )O 1.95 F 0.05 A layered sodium-ion battery cathode material was prepared at -1000℃ for 12 hours; and a sodium-ion coin cell containing this material was prepared.

[0054] Example 6

[0055] The mixed materials were placed in a corundum sagger and sintered at 950°C at a rate of 2°C / min for 15 hours. Other experimental procedures were the same as in Example 1. Na(Ni) was finally obtained. 0.3 Fe 0.3 Mn 0.3 Cu 0.05 Ti 0.05 )O 1.95 F 0.05 A layered sodium-ion battery cathode material was prepared at -950℃ for 15 hours; and a sodium-ion coin cell containing this material was prepared.

[0056] Comparative Example 1

[0057] The additive was added in a molar ratio, i.e., the sum of nickel, iron, and manganese in the precursor: copper sulfate: titanium dioxide = 1:0.05:0.05; other experimental procedures were the same as in Example 1. Finally, fluorine-free (F)-doped Na(Ni) was obtained. 0.3 Fe 0.3 Mn 0.3 Cu 0.05 Ti 0.05 A layered sodium-ion battery cathode material containing O2 was developed; and a sodium-ion coin cell containing this material was prepared.

[0058] Comparative Example 2

[0059] The additives were added in a molar ratio of nickel, iron, and manganese in the precursor to copper sulfate = 1:0.1. Other experimental procedures were the same as in Example 1. Finally, Na(Ni) without titanium (Ti) and fluorine (F) doping was obtained. 0.3 Fe 0.3 Mn 0.3 Cu 0.1 A layered sodium-ion battery cathode material containing O2 was developed; and a sodium-ion coin cell containing this material was prepared.

[0060] Comparative Example 3

[0061] The additives were added in a molar ratio of nickel, iron, and manganese in the precursor to titanium dioxide = 1:0.1. Other experimental procedures were the same as in Example 1. Finally, copper (Cu) and fluorine (F)-free Na(Ni) was obtained. 0.3 Fe 0.3 Mn 0.3 Ti 0.1 A layered sodium-ion battery cathode material containing O2 was developed; and a sodium-ion coin cell containing this material was prepared.

[0062] Comparative Example 4

[0063] No additives were added, and other experimental procedures were the same as in Example 1. Finally, Na(Ni) doped with cations (Cu, Ti) and anions (F) was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 A layered sodium-ion battery cathode material containing O2 was developed; and a sodium-ion coin cell containing this material was prepared.

[0064] Implementation effect analysis

[0065] (1) Material characterization

[0066] The surface morphology and elemental analysis of the sodium-ion cathode materials in Example 1 and Comparative Example 4 were performed using scanning electron microscopy. The test results are as follows: Figure 2 As shown in Table 1.

[0067] Figure 2 These are SEM images of the material. In the images, the top left and bottom left images are both magnified 1000x, while the top right and bottom right images are both magnified 2000x. From... Figure 2 As can be seen, the particles in Example 1, after synergistic doping, exhibit rounded shape and fewer surface defects, reducing side reactions generated by the subsequent materials in the electrolyte, which is a more ideal state for the material. In contrast, the particles in Comparative Example 4 are of varying sizes and irregular shapes, significantly different from those in Example 1. This material will exhibit more side reactions in the electrolyte, affecting the battery cell's electrical performance.

[0068] Table 1. Summary of EDS test results of sodium-ion battery cathode materials in Example 1 and Comparative Example 4

[0069]

[0070] Table 1 shows the EDS data of the materials. After normalization, it can be seen that the content of main elements and dopants in the materials of Example 1 and Comparative Example 4 are in line with the experimental expectations.

[0071] The residual alkali (CO3) in the material was determined by point titration using anhydrous ethanol as the solvent. 2- and OH - The content of ) was tested, and the test results are shown in Table 2 below.

[0072] Table 2 Summary of test results for residual alkali content in different sodium-ion battery cathode materials

[0073]

[0074] As can be seen from the data in Table 2, the sodium-ion battery cathode material prepared using the method of this invention effectively reduces the residual alkali content, which has a profound impact on the cathode slurry preparation process and the electrical performance of the entire battery. High residual alkali content increases the viscosity of the cathode slurry, resulting in a jelly-like consistency, making coating impossible or causing unstable coating density. It also deteriorates the cathode slurry, leading to adverse effects such as subsequent side reactions, which in turn affect the consistency and electrical performance of the battery.

[0075] (2) Sodium-ion battery performance test

[0076] Using a battery testing system, the test voltage was set to 2.0~4.0V. The electrical performance of the sodium-ion button batteries in Examples 1~6 and Comparative Examples 1~4 was tested, mainly including: (1) Capacity retention rate under different discharge rates: Three discharge rates were set, namely: 1C discharge capacity / 0.5C discharge capacity, denoted as 1C / 0.5C, 2C discharge capacity / 0.5C discharge capacity, denoted as 2C / 0.5C, and 3C discharge capacity / 0.5C discharge capacity, denoted as 3C / 0.5C. Wherein, C is the battery charge / discharge rate parameter, defined as the ratio of charging / discharging current to the rated capacity of the battery. Its calculation follows the formula: charge / discharge rate = charging / discharging current (A) / rated capacity (Ah). For example, a battery with a rated capacity of 20Ah corresponds to a 0.5C rate when discharged at 10A. (2) Capacity retention rate after 100 cycles at 25℃ and a discharge rate of 0.5C. The charge and discharge rates are both set to 0.5C, denoted as 0.5C / 0.5C. Capacity retention rate = (discharge capacity of the 100th cycle) / (discharge capacity of the 1st cycle). The test results are shown in Table 3 below. Figure 3 and Figure 4 As shown.

[0077] Table 3. Summary of performance test results of sodium-ion batteries containing different sodium-ion battery cathode materials

[0078]

[0079] From Table 3 and Figure 3 and Figure 4 As can be seen, doping with the three elements effectively improves the rate performance of sodium-ion cathode materials, especially their ability to discharge at high rates. Figure 3 This is mainly due to the improved electronic conductivity of the doped material and the effectively expanded interlayer spacing, which facilitates the insertion and extraction of sodium ions. The doped sodium cathode material exhibits significantly improved cycle performance. Ti inhibits transition metal dissolution and F formation of a passivation layer, synergistically reducing the dissolution of transition metal ions and electrolyte decomposition, effectively improving the interfacial stability and cycle life of the sodium cathode material. Figure 4 ).

[0080] In summary, compared to Na(Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 The method for preparing sodium-ion battery cathode material provided by this invention involves (1) doping with high-valence transition metal ions (Ti). 4+ (2) Cu 2+ Doping can effectively improve the electronic conductivity of materials and suppress Mn. 3+ Dissolution effectively improves rate performance; (3) F - Doping enhances the binding energy between cations and anions, stabilizes the overall structure, and improves the cycle performance of sodium-ion battery cathode materials. Doping with a single element only improves one aspect of the material's performance (e.g., Ti doping improves structural stability but may reduce electronic conductivity; Cu doping improves conductivity but has limited effect on structural stability; F doping improves interfacial stability but may increase synthesis difficulty). However, ternary synergistic doping of Cu + Ti + F achieves complementary advantages and synergistic performance, ultimately yielding sodium-ion battery cathode materials with excellent overall performance.

[0081] Therefore, the sodium-ion battery cathode material prepared using the sodium-ion battery cathode material provided by this invention can be used as a cathode active material in sodium-ion batteries, which can significantly improve the electrical performance of sodium batteries, and this is of great significance for the future development of batteries.

[0082] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a sodium-ion battery cathode material, characterized in that, A sodium-ion battery positive electrode material is prepared by using a sodium battery positive electrode precursor, a sodium source and an additive as raw materials, mixing the raw materials, sintering to obtain a sintered material, cooling, rough crushing, pulverizing, sieving and removing magnetism 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2, and the additive comprises a copper source, a titanium source and a fluorine source. The molar ratio of the sum of nickel, iron, and manganese, sodium source, copper source, titanium source, and fluorine source in the sodium-ion battery cathode precursor is 1: 1.01~1.08: 0.02~0.08: 0.02~0.08: 0.02~0.08; The sintering temperature is 950~1000℃, and the sintering time is 10~15h; The sintered material is subjected to coarse crushing after being naturally cooled to 70~100℃, and the sieve used for screening has a mesh size of 200~400 mesh. The general chemical formula of the sodium-ion battery cathode material is Na(Ni) 0.3 Fe 0.3 Mn 0.3 Cu x Ti 0.1-x )O 2-y F y , where x = 0.04~0.06, y = 0.04~0.

05.

2. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The sodium source includes sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium nitrate, or sodium sulfate; the copper source includes copper sulfate, copper chloride, or copper oxide; the titanium source includes titanium dioxide, titanium tetrachloride, or titanium trichloride; and the fluorine source includes sodium fluoride.

3. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The median particle size D50 of the sodium-ion cathode precursor is 4~15μm. It is prepared by first adding nickel source, manganese source and iron source in a molar ratio of 1:1:1 to the bottom liquid for co-precipitation reaction, aging to obtain a reaction solution containing nickel manganese iron hydroxide, then separating the reaction solution into solid and liquid to obtain crude nickel manganese iron hydroxide, and then preparing the crude nickel manganese iron hydroxide by alkaline washing, water washing and drying.

4. The method for preparing the sodium-ion battery cathode material according to claim 3, characterized in that, The nickel source includes at least one of nickel sulfate, nitrate, and chloride; the manganese source includes at least one of manganese sulfate, nitrate, and chloride; the iron source includes at least one of iron sulfate, nitrate, and chloride; the base solution consists of a complexing agent aqueous solution with a concentration of 0.2~2.5 mol / L and a precipitant aqueous solution with a concentration of 5~20 mol / L, wherein the complexing agent includes at least one of ammonia, sodium citrate, disodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate; and the precipitant includes sodium hydroxide or sodium carbonate.

5. The application of the sodium-ion battery cathode material prepared by the method for preparing the sodium-ion battery cathode material according to claim 1 in a sodium-ion battery.

6. The application of the sodium-ion battery positive electrode material prepared by the method for preparing sodium-ion battery positive electrode material according to claim 5 in sodium-ion batteries, characterized in that, The sodium-ion battery includes a positive electrode sheet containing an active material, which is the positive electrode material of the sodium-ion battery.

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