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

Abstract

The invention discloses a sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery. The preparation method comprises the following steps: mixing a nickel-manganese precursor with a sodium salt and a scandium source, and sintering at high temperature to obtain the sodium ion battery positive electrode material. According to the method disclosed by the invention, special charge polaron can be introduced by utilizing the doping of scandium (Sc) to nickel sites and the change of a crystal structure, so that the stability of a transition metal layer frame structure in the layered oxide is enhanced, the mechanical property of the material is improved, the electronic conductivity and the ion diffusion property of the material are improved, and the irreversible phase change of the material is relieved. A battery assembled by adopting the prepared sodium ion battery positive electrode material has excellent rate capability and capacity retention rate.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and relates to a cathode material for a sodium-ion battery, a preparation method thereof, and a sodium-ion battery. Background Art

[0002] The rapid development of lithium-ion batteries has provided great convenience for our lives. However, the limited reserves of lithium resources have led to an increasing cost of power batteries. In contrast, sodium-ion batteries have a working principle similar to that of lithium-ion batteries, and sodium resources are abundant and easily accessible, having good application prospects in the new energy industry and playing the role of a lithium battery substitute.

[0003] Layered oxides, Prussian blue analogs, and polyanionic materials have been reported as potential cathode materials for sodium-ion batteries. Among them, nickel-manganese-based layered oxides are promising cathode materials. However, their structures will be damaged in the state of deep sodium deintercalation, and complex phase changes occur during the charge and discharge process, resulting in a decline in the rate performance and capacity retention rate of the battery.

[0004] CN117117197A discloses a nickel-manganese-based layered oxide cathode material for a sodium-ion battery and a preparation method thereof. The chemical general formula of the nickel-manganese-based layered oxide cathode material is Na x L y [Ni a Mn b M c N d O 2+δ-γ F γ , where 0.5 ≤ x ≤ 0.8, 0 < y ≤ 0.2, a + b + c + d = 1, 0 < a ≤ 0.5, 0 < c ≤ 0.3, 0 ≤ d < 0.3, -0.2 ≤ δ ≤ 0.2, 0 ≤ γ ≤ 0.2; L is an element for doping and substituting Na at the alkali metal site, and the ion of L is K + ; M is an element for doping and substituting Ni or Mn at the transition metal site, and the ions of M specifically include Mg 2+ , Zn 2+ , Li + any one of them; N is an element for doping and substituting Ni or Mn at the transition metal site, and the ions of N specifically include Nb 5+ , Ca 2+ , B 3+ , Co 3+ , Fe 3+ , Cu 2+ , Al 3+ , Co 2+ , Zr 4+ , Sn 4+ , Ti 4+ , Ru 4+, Nb 4+ 、Te 6+ , Sb 5+ Or Mo 6+ One or more of the above. The nickel-manganese-based layered oxide positive electrode material is used in sodium-ion batteries, which can stably operate at high voltages between 2V and 4.5V, have high specific capacity at high rates, and have good safety and cycle stability. However, the capacity retention rate of sodium-ion batteries can reach 90% after 120 cycles at 1C, and its performance needs to be further improved.

[0005] Therefore, providing a sodium ion battery positive electrode material with good rate performance and capacity retention is a technical problem that needs to be solved urgently. Summary of the invention

[0006] In view of the above technical problems existing in the prior art, the object of the present invention is to provide a sodium ion battery positive electrode material and a preparation method thereof and a sodium ion battery.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a positive electrode material for a sodium ion battery, the preparation method comprising the following steps:

[0009] The nickel-manganese precursor is mixed with sodium salt and scandium source and sintered at high temperature to obtain the positive electrode material of the sodium ion battery.

[0010] The method of the present invention utilizes scandium (Sc) doping on nickel sites, and the change in crystal structure can introduce special charge polarons, which not only enhances the stability of the transition metal layer framework structure in the layered oxide and improves the mechanical properties of the material, but also improves the electronic conductivity and ion diffusion properties of the material, and alleviates the irreversible phase change of the material. The battery assembled with the prepared sodium ion battery positive electrode material has excellent rate performance and capacity retention rate.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, the particle size D50 of the sodium ion battery positive electrode material precursor is 4-10 μm, for example, it can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or 10 μm.

[0013] Preferably, the sodium source comprises sodium carbonate.

[0014] Preferably, the scandium source comprises scandium sulfate.

[0015] Preferably, the average fiber diameter of the titanium dioxide fiber is 50nm-1000nm, for example, it can be 50nm, 100nm, 150nm, 200nm, 300nm, 400nm, 450nm, 500nm, 600nm, 650nm, 700nm, 800nm, 900nm or 1000nm.

[0016] Preferably, based on the total mass of the sodium ion battery positive electrode material precursor as 100wt%, the mass proportion of the scandium element in the scandium source is 2-8wt%, for example, it can be 2wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt% or 8wt%, etc.

[0017] Preferably, the raw materials used for mixing also include titanium dioxide fibers.

[0018] In one embodiment, a nickel-manganese precursor is mixed with a sodium salt, a scandium source and titanium dioxide fibers, and then sintered at a high temperature to obtain a positive electrode material for a sodium ion battery.

[0019] In this preferred technical solution, a scandium source and titanium dioxide fibers are simultaneously introduced during the precursor sodium sintering stage, which not only realizes Sc doping of the material, but also can regulate the positive electrode material to construct a stable fiber layer on the surface and near the surface, which is beneficial to improving the material's stability and sodium ion transportability.

[0020] Preferably, the mass ratio of the scandium source to the titanium dioxide fiber is (6-10):1, for example, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1 or 10:1, etc. Within this preferred range, the stability of the positive electrode material and the sodium ion transport performance can be better regulated, thereby better balancing the rate performance and the cycle performance.

[0021] Preferably, the mixing method is wet mixing, a solvent is used in the mixing process, and the mixing method includes: mixing a sodium ion battery positive electrode material precursor with a sodium salt, a scandium source and a solvent, and then heating and drying to volatilize the solvent.

[0022] In one embodiment, the mixing method comprises: mixing a sodium ion battery positive electrode material precursor with a sodium salt, a scandium source, titanium dioxide fibers and a solvent, and then heating and drying to volatilize the solvent.

[0023] The wet mixing method is beneficial to improving the uniformity of the mixture.

[0024] Preferably, the heating and drying temperature is 60-90°C, for example, it can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C.

[0025] Preferably, the high temperature sintering temperature is 600-1000°C, for example, it may be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C.

[0026] Preferably, the high temperature sintering time is 6-10 h, for example, it can be 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h or 10 h.

[0027] As a preferred technical solution of the method of the present invention, the method for preparing the nickel-manganese precursor comprises the following steps:

[0028] The mixed metal salt solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel to carry out a co-precipitation reaction to obtain the nickel-manganese precursor.

[0029] Preferably, the total concentration of metal ions in the mixed metal salt solution is 1.5-3 mol / L, for example, it can be 1.5 mol / L, 1.7 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.5 mol / L, 2.7 mol / L, 2.8 mol / L or 3 mol / L, etc.

[0030] Preferably, the precipitant solution is a sodium hydroxide solution.

[0031] Preferably, the complexing agent solution is aqueous ammonia.

[0032] Preferably, the mass concentration of the precipitant solution is 30-35%, for example, it can be 30%, 31%, 32%, 33%, 34% or 35%.

[0033] Preferably, the mass concentration of the complexing agent solution is 10-20%, for example, it can be 10%, 12%, 13%, 14%, 15%, 16%, 18% or 20%.

[0034] Preferably, the feed rate of the mixed metal salt solution is 10-80 L / h, for example, it can be 10 L / h, 12 L / h, 15 L / h, 18 L / h, 20 L / h, 25 L / h, 30 L / h, 35 L / h, 40 L / h, 45 L / h, 50 L / h, 55 L / h, 60 L / h, 65 L / h, 70 L / h, 75 L / h or 80 L / h, etc.

[0035] Preferably, the flow rate of the precipitant solution is 2-20 L / h, for example, it can be 2 L / h, 3 L / h, 4 L / h, 6 L / h, 8 L / h, 9 L / h, 10 L / h, 12 L / h, 13 L / h, 14 L / h, 15 L / h, 16 L / h, 18 L / h or 20 L / h, etc.

[0036] Preferably, the flow rate of the complexing agent solution is 2-10 L / h, for example, it can be 2 L / h, 3 L / h, 4 L / h, 6 L / h, 8 L / h, 9 L / h or 10 L / h.

[0037] Preferably, the pH value of the base solution is 10-12, for example, it can be 10, 10.2, 10.5, 10.7, 10.8, 11, 11.5, 11.8 or 12.

[0038] Preferably, the ammonia concentration in the base liquid is 4-10 g / L, for example, it can be 4 L / h, 6 L / h, 8 L / h, 9 L / h or 10 L / h.

[0039] Preferably, the temperature of the base liquid is 40-80°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C.

[0040] Preferably, during the coprecipitation reaction, the pH value of the reaction system is 9-11, for example, it can be 9, 9.2, 9.4, 9.5, 9.7, 9.8, 10, 10.2, 10.4, 10.5, 10.6, 10.8 or 11.

[0041] Preferably, the coprecipitation reaction is accompanied by stirring, and the stirring speed is 200-400 rpm, for example, it can be 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, 325 rpm, 350 rpm, 370 rpm, 380 rpm or 400 rpm.

[0042] Preferably, during the coprecipitation reaction, the ammonia concentration of the reaction system is 3-8 g / L, for example, 3 g / L, 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L, 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L or 8 g / L.

[0043] Preferably, during the coprecipitation reaction, the temperature of the reaction system is 40-60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C.

[0044] In a second aspect, the present invention provides a sodium ion battery positive electrode material prepared by the method described in the first aspect.

[0045] In a third aspect, the present invention provides a sodium ion battery, comprising a positive electrode, a negative electrode and a separator, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode comprises the sodium ion battery positive electrode material described in the second aspect.

[0046] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The method of the present invention utilizes scandium (Sc) doping on nickel sites, and the change in crystal structure can introduce special charge polarons, which not only enhances the stability of the transition metal layer framework structure in the layered oxide and improves the mechanical properties of the material, but also improves the electronic conductivity and ion diffusion properties of the material, and alleviates the irreversible phase change of the material. The battery assembled with the prepared sodium ion battery positive electrode material has excellent rate performance and capacity retention rate. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0050] Example 1

[0051] This embodiment provides a method for preparing a positive electrode material for a sodium ion battery, comprising the following steps:

[0052] Step 1: prepare a 2 mol / L mixed salt solution of nickel sulfate and manganese sulfate at a metal molar ratio of 1:1, use 32% industrial liquid alkali as a precipitant, and 15% ammonia water as a complexing agent.

[0053] Step 2: Add pure water, liquid alkali and ammonia water to a 1000L reactor to prepare a base liquid, and introduce N2 as a protective gas. The pH of the base liquid is adjusted to 11, the ammonia concentration is adjusted to 8g / L, the temperature is controlled at 60°C, and the stirring speed is adjusted to 300rpm.

[0054] Step 3, adding the mixed salt solution, precipitant and complexing agent into the reactor in parallel, with flow rates of 40 L / h, 10 L / h and 3 L / h respectively; during the reaction, the flow rate was adjusted to keep the pH between 10-11, the ammonia concentration was 3-5 g / L, the reaction temperature was maintained at 50°C, and the stirring speed was adjusted to 350 rpm.

[0055] Step 4: After D50 reaches the target particle size of 5 μm, the feeding is stopped, and centrifugal washing, drying, screening, iron removal, and packaging are performed to obtain a nickel-manganese-based precursor.

[0056] Step 5: Fully mix the nickel-manganese precursor with a sodium source (sodium carbonate), a scandium source (scandium sulfate) and ethanol, wherein the mass ratio of the scandium element to the nickel-manganese precursor is 2wt%. The ethanol is dried at 80°C, and then sintered at 680°C for 8h to obtain a scandium-doped nickel-manganese-based sodium ion battery positive electrode material.

[0057] Example 2

[0058] The difference between Example 2 and Example 1 is that the metal ion concentration of the mixed salt solution is 1.5 mol / L.

[0059] Example 3

[0060] The difference between Example 3 and Example 1 is that the mass proportion of scandium element relative to the nickel-manganese precursor is 4 wt %.

[0061] Example 4

[0062] This embodiment provides a method for preparing a positive electrode material for a sodium ion battery, comprising the following steps:

[0063] Step 1: prepare nickel sulfate and manganese sulfate into a 3 mol / L mixed salt solution at a metal molar ratio of 1:1, use 35% industrial liquid alkali as a precipitant, and 10% ammonia water as a complexing agent.

[0064] Step 2: Add pure water, liquid alkali and ammonia water into the reactor to prepare the base liquid, and introduce N2 as a protective gas. The pH of the base liquid is adjusted to 12, the ammonia concentration is adjusted to 10 g / L, the temperature is controlled at 80°C, and the stirring speed is adjusted to 400 rpm.

[0065] Step 3, adding the mixed salt solution, precipitant and complexing agent to the reactor in parallel, with flow rates of 20 L / h, 5 L / h and 8 L / h respectively; during the reaction, the flow rate was adjusted to keep the pH between 10.5-11, the ammonia concentration was 6-8 g / L, the reaction temperature was maintained at 60°C, and the stirring speed was adjusted to 400 rpm.

[0066] Step 4: After D50 reaches the target particle size of 10 μm, the feeding is stopped, and centrifugal washing, drying, screening, iron removal, and packaging are performed to obtain a nickel-manganese-based precursor.

[0067] Step 5: Fully mix the nickel-manganese precursor with a sodium source (sodium carbonate), a scandium source (scandium sulfate) and ethanol, wherein the mass ratio of the scandium element to the nickel-manganese precursor is 6wt%. The ethanol is dried at 80°C and then sintered at 800°C for 7h to obtain a scandium-doped nickel-manganese-based sodium ion battery positive electrode material.

[0068] Example 5

[0069] This embodiment provides a method for preparing a positive electrode material for a sodium ion battery, comprising the following steps:

[0070] Step 1: prepare a 2.5 mol / L mixed salt solution of nickel sulfate and manganese sulfate at a metal molar ratio of 1:1, use 30% industrial liquid alkali as a precipitant, and 20% ammonia water as a complexing agent.

[0071] Step 2: Add pure water, liquid alkali and ammonia water into the reactor to prepare the base liquid, and introduce N2 as a protective gas. The pH of the base liquid is adjusted to 10, the ammonia concentration is adjusted to 4 g / L, the temperature is controlled at 50°C, and the stirring speed is adjusted to 200 rpm.

[0072] Step 3, adding the mixed salt solution, precipitant and complexing agent to the reactor in parallel, with flow rates of 70 L / h, 20 L / h and 10 L / h respectively; during the reaction, the flow rate was adjusted to keep the pH between 9.5-10.5, the ammonia concentration was 5-7 g / L, the reaction temperature was maintained at 50°C, and the stirring speed was adjusted to 350 rpm.

[0073] Step 4: After D50 reaches the target particle size of 7 μm, the feeding is stopped, and centrifugal washing, drying, screening, iron removal, and packaging are performed to obtain a nickel-manganese-based precursor.

[0074] Step 5. Fully mix the nickel-manganese precursor with a sodium source (sodium carbonate), a scandium source (scandium sulfate), titanium dioxide fibers (with an average fiber diameter of 200 nm) and ethanol. The mass ratio of the scandium element to the nickel-manganese precursor is 8 wt %, and the mass ratio of the scandium source to the titanium dioxide fiber is 8:1. Dry the ethanol at 80°C and then sinter at 900°C for 6.5 hours to obtain a scandium-doped nickel-manganese-based sodium ion battery positive electrode material.

[0075] Example 6

[0076] The difference between this embodiment and embodiment 1 is that the amount of titanium dioxide fiber used is changed so that the mass ratio of the scandium source to the titanium dioxide fiber is 4:1.

[0077] Example 7

[0078] The difference between this embodiment and embodiment 1 is that the amount of titanium dioxide fiber used is changed so that the mass ratio of the scandium source to the titanium dioxide fiber is 12:1.

[0079] Comparative Example 1

[0080] The difference between Comparative Example 1 and Example 1 is that scandium element doping is not performed during the sintering process.

[0081] Battery Assembly:

[0082] 75 wt % of positive electrode active material (the positive electrode materials prepared in each embodiment and comparative example are respectively used as positive electrode active material), 10 wt % of Super-P and 15 wt % of polyvinylidene fluoride (PVDF) are dispersed in N-methylpyrrolidone (NMP) solution to prepare positive electrode slurry, which is coated on aluminum foil and dried to obtain a positive electrode;

[0083] The lithium sheet is the negative electrode;

[0084] The separator is a PP microporous membrane (Celgard2400);

[0085] The composition of the electrolyte is: 1M LiPF6 (the solvent is a mixed solvent of EC, DMC and EMC, wherein the volume ratio of EC:DMC:EMC=1:1:1);

[0086] The positive electrode, separator, negative electrode and electrolyte are assembled to obtain a button battery.

[0087] Performance test: The electrochemical performance of the positive electrode material was tested at room temperature, 2.5-4.2V voltage range, and 0.1C rate. The results are shown in Table 1:

[0088] Table 1

[0089]

[0090]

[0091] The method of the present invention can effectively improve the rate performance and cycle performance of the material by doping the nickel-manganese cathode material with a scandium source. Furthermore, by introducing titanium dioxide fiber in the doping step, a stable fiber layer can be constructed on the surface and near the surface of the cathode material, further improving the stability of the material and the sodium ion transportability, so that the electrochemical performance is further improved.

[0092] At the same time, by comparing Example 5 with Examples 6-7, it can be seen that excessive or insufficient use of titanium dioxide fiber is not conducive to forming a fiber layer with uniform composition and thickness on the surface of the material, thereby being not conducive to improving the structural stability and ion transmission performance of the material.

[0093] By comparing Example 1 with Comparative Example 1, it can be seen that the doping of Sc element not only enhances the structural stability of the material, but also improves the electronic conductivity and ion diffusion performance of the material, alleviates the irreversible phase change of the material, and is beneficial to improving the rate performance and capacity retention rate of the sodium ion battery positive electrode material.

[0094] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a positive electrode material for a sodium ion battery, characterized in that: The preparation method comprises the following steps: The nickel-manganese precursor is mixed with sodium salt and scandium source and sintered at high temperature to obtain the positive electrode material of the sodium ion battery.

2. The preparation method according to claim 1, characterized in that: The particle size D50 of the sodium ion battery positive electrode material precursor is 4-10 μm; Preferably, the sodium source comprises sodium carbonate; Preferably, the scandium source comprises scandium sulfate; Preferably, the average fiber diameter of the titanium dioxide fiber is 50nm-1000nm.

3. The preparation method according to claim 1 or 2, characterized in that: Based on the total mass of the sodium ion battery positive electrode material precursor being 100wt%, the mass proportion of the scandium element in the scandium source is 2-8wt%; Preferably, the raw materials used for mixing also include titanium dioxide fibers; Preferably, the mass ratio of the scandium source to the titanium dioxide fiber is (6-10):

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that The mixing method is wet mixing, and a solvent is used in the mixing process. The mixing method comprises: mixing a sodium ion battery positive electrode material precursor with a sodium salt, a scandium source and a solvent, and then heating and drying to volatilize the solvent; Preferably, the heating and drying temperature is 60-90°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The high temperature sintering temperature is 600-1000°C; Preferably, the high temperature sintering time is 6-10 hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The method for preparing the nickel-manganese precursor comprises the following steps: The mixed metal salt solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel to carry out a co-precipitation reaction to obtain the nickel-manganese precursor.

7. The preparation method according to claim 6, characterized in that: The total concentration of metal ions in the mixed metal salt solution is 1.5-3 mol / L; Preferably, the precipitant solution is a sodium hydroxide solution; Preferably, the complexing agent solution is aqueous ammonia; Preferably, the mass concentration of the precipitant solution is 30-35%; Preferably, the mass concentration of the complexing agent solution is 10-20%; Preferably, the feed rate of the mixed metal salt solution is 10-80 L / h; Preferably, the flow rate of the precipitant solution is 2-20 L / h; Preferably, the flow rate of the complexing agent solution is 2-10 L / h; Preferably, the pH value of the base liquid is 10-12; Preferably, the ammonia concentration in the base solution is 4-10 g / L; Preferably, the temperature of the base liquid is 40-80°C.

8. The preparation method according to claim 6 or 7, characterized in that: During the coprecipitation reaction, the pH value of the reaction system is 9-11; Preferably, the coprecipitation reaction is accompanied by stirring, and the stirring speed is 200-400 rpm; Preferably, during the coprecipitation reaction, the ammonia concentration of the reaction system is 3-8 g / L; Preferably, during the coprecipitation reaction, the temperature of the reaction system is 40-60°C.

9. A sodium ion battery positive electrode material prepared by the method according to any one of claims 1 to 8.

10. A sodium ion battery, comprising a positive electrode, a negative electrode and a separator, wherein the separator is located between the positive electrode and the negative electrode, characterized in that: The positive electrode comprises the sodium ion battery positive electrode material according to claim 9.

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