Sodium ion battery positive electrode material and preparation method therefor, and sodium ion battery

Abstract

Disclosed in the present application are a sodium ion battery positive electrode material and a preparation method therefor, 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 then sintering at a high temperature to obtain a sodium ion battery positive electrode material. The method of the present application uses doping of a nickel site by scandium (Sc), and special charge polarons can be introduced due to a change in crystal structure, which enhances the stability of a framework structure of a transition metal layer in a layered oxide, and improves the mechanical properties of the material, while also improving the electronic conductivity and ion diffusion properties of the material, and alleviating irreversible phase transition of the material. A battery assembled by using the prepared sodium ion battery positive electrode material has excellent rate performance and capacity retention.

Description

A cathode material for sodium-ion batteries, its preparation method and sodium-ion batteries Technical Field

[0001] This application relates to the technical field of sodium-ion batteries, and relates to a cathode material for sodium-ion batteries, its preparation method and sodium-ion batteries. 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 rich and easy to obtain, having good application prospects in the new energy industry and playing the role of a substitute for lithium batteries.

[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, its structure will be damaged in the deeply sodiated state, 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] CN117117I97A discloses a nickel-manganese-based layered oxide cathode material for sodium-ion batteries and a preparation method. The chemical general formula of the nickel-manganese-based layered oxide cathode material is Na 2+ , 3+ , 2+ , + , 2+ , 3+ , 3+ , 3+ , 5+ , 4+ , 2+ 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 that dopes and replaces Na at the alkali metal site, and the ion of L is K + ; M is an element that dopes and replaces Ni or Mn at the transition metal site, and the ions of M specifically include Mg 2+ , Zn 2+ , Li + any one of; N is an element that dopes and replaces 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+ , Sn4+ Ti 4+ Ru 4+ Nb 4+ Te 6+ Sb 5+ or Mo 6+ The nickel-manganese-based layered oxide positive electrode material can be used for a sodium ion battery, and can stably work at a high voltage of 2V-4.5V, has a high specific capacity at a high rate, and has good safety and cycle stability. However, the capacity retention rate of the sodium ion battery can reach 90% at 1C cycle for 120 cycles, and the performance needs to be further improved.

[0005] Therefore, it is a technical problem to be solved at present to provide a sodium ion battery positive electrode material having good rate performance and capacity retention rate. SUMMARY

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

[0007] In view of the above technical problems existing in the prior art, the purpose of the present application is to provide a sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery.

[0008] To achieve the above purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a preparation method of a sodium ion battery positive electrode material, which comprises the following steps:

[0010] The nickel-manganese precursor is mixed with a sodium salt and a scandium source, and then high-temperature sintering is performed to obtain a sodium ion battery positive electrode material.

[0011] The method of the present application utilizes the doping of scandium (Sc) to the nickel site, and the change of the crystal structure can introduce special charge polarons. Not only the stability of the transition metal layer framework structure in the layered oxide is enhanced, but also the mechanical properties of the material are improved. Moreover, the electronic conductivity and ion diffusion performance of the material are improved, and the irreversible phase transition of the material is relieved. The battery assembled by using the prepared sodium ion battery positive electrode material has excellent rate performance and capacity retention rate.

[0012] The following is an optional technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following optional technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0013] In an embodiment, the particle size D50 of the sodium-ion battery cathode 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, etc.

[0014] In an embodiment, the sodium source comprises sodium carbonate.

[0015] In an embodiment, the scandium source comprises scandium sulfate.

[0016] In an embodiment, the average fiber diameter of the titanium dioxide fiber is 50 nm-1000 nm, for example, it can be 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, 450 nm, 500 nm, 600 nm, 650 nm, 700 nm, 800 nm, 900 nm or 1000 nm, etc.

[0017] In an embodiment, the mass fraction of scandium in the scandium source accounts for 2-8 wt% based on the total mass of the sodium-ion battery cathode material precursor, for example, it can be 2 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt% or 8 wt%, etc.

[0018] In an embodiment, the raw materials for mixing further comprise titanium dioxide fibers.

[0019] In an embodiment, after mixing the nickel-manganese precursor with the sodium salt, the scandium source and the titanium dioxide fiber, high-temperature sintering is performed to obtain a sodium-ion battery cathode material.

[0020] In this preferred technical solution, the scandium source and the titanium dioxide fiber are introduced at the same time in the sintering stage of the precursor with sodium, which not only realizes Sc doping of the material, but also can regulate the construction of a stable fiber layer on the surface and the near-surface layer of the cathode material, which is beneficial to improving the stability and sodium-ion transport property of the material.

[0021] In an embodiment, the mass ratio of the scandium source to the titanium dioxide fiber is (6-10):1, for example, it can be 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 and sodium-ion transport property of the cathode material can be better regulated, so that the rate performance and cycle performance can be better balanced.

[0022] In an embodiment, the mixing method is wet mixing, and the mixing process uses a solvent. The mixing method comprises: mixing the sodium-ion battery positive electrode material precursor, the sodium salt, the scandium source, and the solvent, and then heating and drying to volatilize the solvent.

[0023] In an embodiment, the mixing method comprises: mixing the sodium-ion battery positive electrode material precursor, the sodium salt, the scandium source, the titanium dioxide fiber, and the solvent, and then heating and drying to volatilize the solvent.

[0024] The wet mixing method described above is advantageous in improving the uniformity of the mixture.

[0025] In an embodiment, the heating and drying temperature is 60-90°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C, etc.

[0026] In an embodiment, the high-temperature sintering temperature is 600-1000°C, for example, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or 1000°C, etc.

[0027] In an embodiment, the high-temperature sintering time is 6-10h, for example, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, or 10h, etc.

[0028] As an optional technical solution of the method described in the present application, the preparation method of the nickel-manganese precursor comprises the following steps:

[0029] The mixed metal salt solution, the precipitant solution, and the complexing agent solution are added into the bottom liquid in parallel flow to perform a co-precipitation reaction to obtain the nickel-manganese precursor.

[0030] In an embodiment, the total concentration of metal ions in the mixed metal salt solution is 1.5-3mol / L, for example, 1.5mol / L, 1.7mol / L, 1.8mol / L, 2mol / L, 2.2mol / L, 2.4mol / L, 2.5mol / L, 2.7mol / L, 2.8mol / L, or 3mol / L, etc.

[0031] In an embodiment, the precipitant solution is a sodium hydroxide solution.

[0032] In an embodiment, the complexing agent solution is ammonia water.

[0033] In an embodiment, the mass concentration of the precipitant solution is 30-35%, for example, 30%, 31%, 32%, 33%, 34%, or 35%, etc.

[0034] In one embodiment, 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%, etc.

[0035] In one embodiment, the feeding speed 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.

[0036] In one embodiment, 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.

[0037] In one embodiment, 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, etc.

[0038] In one embodiment, the pH value of the bottom 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, etc.

[0039] In one embodiment, the ammonia concentration in the bottom solution 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, etc.

[0040] In one embodiment, the temperature of the bottom solution is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃, etc.

[0041] In one embodiment, during the process of the co-precipitation 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, etc.

[0042] In one embodiment, the co-precipitation reaction is accompanied by stirring, and the stirring speed is 200-400 rpm, for example, 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, 325 rpm, 350 rpm, 370 rpm, 380 rpm or 400 rpm.

[0043] In one embodiment, the ammonia concentration of the reaction system during the co-precipitation reaction 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, etc.

[0044] In one embodiment, the temperature of the reaction system during the co-precipitation reaction is 40-60℃, for example, 40℃, 45℃, 50℃, 55℃ or 60℃, etc.

[0045] In a second aspect, the application provides a sodium ion battery positive electrode material prepared by the method of the first aspect.

[0046] In a third aspect, the application provides a sodium ion battery, comprising a positive electrode, a negative electrode and a separator, the separator is located between the positive electrode and the negative electrode, and the positive electrode comprises the sodium ion battery positive electrode material of the second aspect.

[0047] The numerical ranges described herein also include any and all point values and sub-ranges contained therein. Due to the language of the specification, the numerical ranges are inclusive of their endpoints.

[0048] Compared with the prior art, the application has the following beneficial effects:

[0049] The method of the application utilizes the doping of scandium (Sc) to the nickel site, and the change in the 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 performance of the material, and alleviates the irreversible phase transition of the material. The battery assembled by using the prepared sodium ion battery positive electrode material has excellent rate performance and capacity retention rate.

[0050] Other aspects can become apparent from the following detailed description, when read in conjunction with the drawings. DETAILED DESCRIPTION

[0051] The technical solutions of the application are further illustrated below by means of specific embodiments.

[0052] Example 1

[0053] The embodiment provides a preparation method of a sodium ion battery positive electrode material.

[0054] Step 1, nickel sulfate and manganese sulfate are prepared into a mixed salt solution with a metal molar ratio of 1:1 and a concentration of 2 mol / L, 32% industrial liquid alkali is used as a precipitant, and 15% ammonia water is used as a complexing agent.

[0055] Step 2, a bottom solution is prepared by adding pure water, liquid alkali and ammonia water into a 1000L reaction kettle, N2 is introduced as a protective gas, the pH of the bottom solution is adjusted to 11, the ammonia concentration is adjusted to 8g / L, the temperature is controlled at 60℃, and the stirring speed is adjusted to 300rpm.

[0056] Step 3, the mixed salt solution, the precipitant and the complexing agent are added into the reaction kettle in parallel flow, and the flow rates are 40L / h, 10L / h and 3L / h respectively; during the reaction, the pH is kept between 10 and 11 by adjusting the flow rate, the ammonia concentration is 3-5g / L, the reaction temperature is maintained at 50℃, and the stirring speed is adjusted to 350rpm.

[0057] Step 4, after the D50 reaches the target particle size of 5um, the feeding is stopped, centrifugal washing, drying, screening, iron removal, packaging are carried out, and a nickel-manganese-based precursor is obtained.

[0058] Step 5, the nickel-manganese precursor is mixed with a sodium source (sodium carbonate), a scandium source (scandium sulfate) and ethanol, the mass ratio of scandium element to the nickel-manganese precursor is 2wt%, the ethanol is dried at 80℃, and then sintered at 680℃ for 8h, to obtain a scandium-doped nickel-manganese-based sodium ion battery positive electrode material.

[0059] Example 2

[0060] The difference between example 2 and example 1 is that the metal ion concentration of the mixed salt solution is 1.5mol / L.

[0061] Example 3

[0062] The difference between example 3 and example 1 is that the mass ratio of scandium element to the nickel-manganese precursor is 4wt%.

[0063] Example 4

[0064] The embodiment provides a preparation method of a sodium ion battery positive electrode material, comprising the following steps:

[0065] Step 1, nickel sulfate and manganese sulfate are prepared into a mixed salt solution with a metal molar ratio of 1:1 and a concentration of 3 mol / L, 35% industrial liquid alkali is used as a precipitant, and 10% ammonia water is used as a complexing agent.

[0066] Step 2, prepare the bottom solution by adding pure water, liquid alkali and ammonia water into the reaction kettle, and introduce N2 as protective gas, adjust the pH of the bottom solution to 12, adjust the ammonia concentration to 10 g / L, control the temperature at 80℃, and adjust the stirring speed to 400 rpm.

[0067] Step 3, the mixed salt solution, precipitant and complexing agent are added into the reaction kettle in parallel flow, the flow rates are 20 L / h, 5 L / h and 8 L / h respectively; during the reaction, the pH is maintained at 10.5-11 by adjusting the flow rate, the ammonia concentration is 6-8 g / L, the reaction temperature is maintained at 60℃, and the stirring speed is adjusted to 400 rpm,

[0068] Step 4, stop feeding when D50 reaches the target particle size of 10 μm, perform centrifugal washing, drying, screening, iron removal, packaging, and obtain the nickel-manganese-based precursor.

[0069] Step 5, mix the nickel-manganese precursor with sodium source (sodium carbonate), scandium source (scandium sulfate) and ethanol, the mass fraction of scandium element relative to the nickel-manganese precursor is 6wt%, dry the ethanol at 80℃, and then sinter at 800℃ for 7h to obtain the scandium-doped nickel-manganese-based sodium ion battery positive electrode material.

[0070] Example 5

[0071] The embodiment provides a preparation method of a sodium ion battery positive electrode material, comprising the following steps:

[0072] Step 1, prepare a mixed salt solution with a metal molar ratio of 1:1 by mixing nickel sulfate and manganese sulfate into 2.5 mol / L, use 30% industrial liquid alkali as a precipitant, and use 20% ammonia water as a complexing agent.

[0073] Step 2, prepare the bottom solution by adding pure water, liquid alkali and ammonia water into the reaction kettle, and introduce N2 as protective gas, adjust the pH of the bottom solution to 10, adjust the ammonia concentration to 4 g / L, control the temperature at 50℃, and adjust the stirring speed to 200 rpm.

[0074] Step 3, the mixed salt solution, precipitant and complexing agent are added into the reaction kettle in parallel flow, the flow rates are 70 L / h, 20 L / h and 10 L / h respectively; during the reaction, the pH is maintained at 9.5-10.5 by adjusting the flow rate, the ammonia concentration is 5-7 g / L, the reaction temperature is maintained at 50℃, and the stirring speed is adjusted to 350 rpm,

[0075] Step 4, stop feeding when D50 reaches the target particle size of 7 μm, perform centrifugal washing, drying, screening, iron removal, packaging, and obtain the nickel-manganese-based precursor.

[0076] Step 5, the nickel-manganese precursor is mixed with a sodium source (sodium carbonate), a scandium source (scandium sulfate), titanium dioxide fibers (average fiber diameter of 200 nm) and ethanol, the mass ratio of scandium element to the nickel-manganese precursor is 8wt%, the mass ratio of the scandium source to the titanium dioxide fibers is 8:1, the ethanol is dried at 80°C, and then sintered at 900°C for 6.5h to obtain a scandium-doped nickel-manganese-based sodium-ion battery positive electrode material.

[0077] Example 6

[0078] The difference between this example and Example 1 is that the amount of titanium dioxide fibers used is changed, so that the mass ratio of the scandium source to the titanium dioxide fibers is 4:1.

[0079] Example 7

[0080] The difference between this example and Example 1 is that the amount of titanium dioxide fibers used is changed, so that the mass ratio of the scandium source to the titanium dioxide fibers is 12:1.

[0081] Comparative Example 1

[0082] The difference between Comparative Example 1 and Example 1 is that the scandium element is not doped during the sintering process.

[0083] Battery assembly:

[0084] 75wt% of the positive electrode active material (the positive electrode material prepared in each example and comparative example is the positive electrode active material), 10wt% of Super-P and 15wt% of polyvinylidene fluoride (PVDF) are dispersed in an N-methyl pyrrolidone (NMP) solution to prepare a positive electrode slurry, which is coated on an aluminum foil and dried to obtain a positive electrode;

[0085] A lithium sheet is used as the negative electrode;

[0086] The separator is a PP microporous membrane (Celgard 2400);

[0087] 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);

[0088] The above positive electrode, separator, negative electrode and electrolyte are assembled to obtain a button cell.

[0089] Performance test: the electrochemical performance of the positive electrode material is tested at room temperature, in the voltage range of 2.5-4.2V, and at a rate of 0.1C. The results are shown in Table 1:

[0090] Table 1

[0091] The method of the present application can effectively improve the rate performance and cycle performance of the nickel-manganese positive electrode material by doping the nickel-manganese positive electrode material with a scandium source. Further, the introduction of titanium dioxide fibers in the doping step can construct a stable fiber layer on the surface and near-surface of the positive electrode material, further improving the stability and sodium ion transport performance of the material, so that the electrochemical performance is further improved.

[0092] Meanwhile, through the comparison of Example 5 and Examples 6-7, it can be known that too much or too little of the titanium dioxide fibers is not conducive to forming a fiber layer with uniform composition and thickness on the surface of the material, thereby not conducive to improving the structural stability and ion transport performance of the material.

[0093] Through the comparison of Example 1 and Comparative Example 1, it can be known 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 transition of the material, and is conducive to improving the rate performance and capacity retention rate of the sodium ion battery positive electrode material.

[0094] The applicant declares that the above examples are used to illustrate the detailed method of the present application, but the present application is not limited to the above detailed method, that is, the present application does not mean that it must rely on the above detailed method to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a sodium-ion battery cathode material, comprising the following steps: mixing a nickel-manganese precursor with a sodium salt and a scandium source, and then high-temperature sintering to obtain the sodium-ion battery cathode material.

2. The production method according to claim 1, wherein, The particle size D50 of the sodium-ion battery cathode material precursor is 4-10 μm. Optionally, the sodium source comprises sodium carbonate. Optionally, the scandium source comprises scandium sulfate. Optionally, the average fiber diameter of the titanium dioxide fiber is 50-1000 nm.

3. The production method according to claim 1 or 2, wherein The mass fraction of scandium in the scandium source is 2-8 wt% based on the total mass of the sodium-ion battery cathode material precursor. Optionally, the raw materials for mixing further comprise titanium dioxide fiber. Optionally, the mass ratio of the scandium source to the titanium dioxide fiber is (6-10) :

1.

4. The production process according to any one of claims 1 to 3, wherein The mixing is performed by wet mixing, and a solvent is used in the mixing process, and the mixing method comprises: mixing the sodium-ion battery cathode material precursor with the sodium salt, the scandium source and the solvent, and then heating and drying to volatilize the solvent. Optionally, the heating and drying temperature is 60-90℃.

5. The production process according to any one of claims 1 to 4, wherein The high-temperature sintering temperature is 600-1000℃. Optionally, the high-temperature sintering time is 6-10 h.

6. The method of making according to any one of claims 1-5, wherein, 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 into the bottom liquid in parallel flow to perform a co-precipitation reaction to obtain the nickel-manganese precursor.

7. The production method according to claim 6, wherein The total concentration of metal ions in the mixed metal salt solution is 1.5-3 mol / L. Optionally, the precipitant solution is sodium hydroxide solution. Optionally, the complexing agent solution is ammonia water. Optionally, the mass concentration of the precipitant solution is 30-35%. Optionally, the mass concentration of the complexing agent solution is 10-20%. Optionally, the feeding speed of the mixed metal salt solution is 10-80 L / h. Optionally, the flow rate of the precipitant solution is 2-20 L / h. Optionally, the flow rate of the complexing agent solution is 2-10 L / h. Optionally, the pH value of the bottom liquid is 10-12. Optionally, the ammonia concentration in the bottom liquid is 4-10 g / L. Optionally, the temperature of the bottom liquid is 40-80℃.

8. The production method according to claim 6 or 7, wherein During the co-precipitation reaction, the pH value of the reaction system is 9-11. Optionally, the co-precipitation reaction is accompanied by stirring, and the stirring speed is 200-400 rpm. Optionally, during the co-precipitation reaction, the ammonia concentration in the reaction system is 3-8 g / L. Optionally, during the co-precipitation reaction, the temperature of the reaction system is 40-60℃. 9.A sodium-ion battery cathode material prepared by the method of any one of claims 1-8.

10. A sodium-ion battery comprising a positive electrode, a negative electrode, and a separator membrane, the separator membrane being located between the positive electrode and the negative electrode, wherein, The positive electrode comprises the sodium-ion battery cathode material of claim 9.

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