CN115966687A - A kind of layered sodium ion battery cathode material and its preparation method and application - Google Patents

Abstract

The invention provides a layered sodium-ion battery anode material and a preparation method and application thereof, wherein the chemical formula of the layered sodium-ion battery anode material is Na _a Mg _b Cu _x Fe _y Mn _z O ₂ Wherein a +2x, 3y, 4z, 2b, 4 is more than or equal to 0.85 and less than or equal to 0.95 of a, more than or equal to 0.05 and less than or equal to 0.1 of b, x>0，y>0，z>The valence of 0,Mn is +4, and the invention dopes a proper amount of magnesium in the sodium ion anode material, which can not only lead trivalent manganese in the materialCompletely oxidized into tetravalent manganese and can inhibit Mn at low potential ⁴⁺ Reduction of (2).

Description

A kind of layered sodium ion battery cathode material and its preparation method and application

technical field

The invention belongs to the technical field of sodium ion batteries, and relates to a layered sodium ion battery positive electrode material, a preparation method and application thereof.

Background technique

比Li⁺半径

更大，Na⁺脱出和嵌入引起的复杂相变通常导致其循环稳定性相对较差，同时也会影响其倍率性能；因此，探索具有高倍率和长循环稳定性的钠离子电池正极材料是非常必要的。One of the key challenges for the practical application of layered oxide cathode materials for sodium-ion batteries is to improve the cycle stability of the materials. Na ⁺ radius

than Li ⁺ radius

Larger, complex phase transitions caused by Na ⁺ deintercalation and intercalation usually lead to relatively poor cycle stability and also affect their rate performance; therefore, it is very important to explore cathode materials for Na-ion batteries with high rate and long cycle stability. necessary.

Elemental doping has been widely used to enhance the electrochemical performance of transition metal oxide layered cathode materials. However, due to the differences in ionic radius, valence state, and electrochemical activity, the effect and improvement mechanism of introducing doping elements are still not very clear. Understanding how doping elements tune the crystal and electronic structures to improve electrochemical performance is important for revealing the structure-property relationship and rationally designing high-performance cathode materials. Mg ²⁺ doping has been proved to be an effective means to effectively improve the performance of layered oxide cathode materials.

CN115611319A discloses a copper-iron-manganese-based positive electrode material for a sodium ion battery and a preparation method thereof. The preparation method includes the following steps: S1 dissolving sodium source, copper source, iron source, manganese source and dopant source M in deionized water, and then Add fuel and stir evenly to obtain a mixed solution; S2 put the mixed solution in a muffle furnace for self-propagating combustion, the self-propagating combustion is to first raise the temperature of the muffle furnace to 300-500°C, Put it in a muffle furnace, and burn the mixed solution violently in an oxygen-containing atmosphere for 1-60 minutes to obtain a precursor; S3 calcines the precursor at 600-900°C for 1-10h, the material is obtained.

CN109817974A discloses a sodium ion nickel-manganese-magnesium-iron quaternary positive electrode material and its preparation method. The chemical molecular formula of the positive electrode material is Na _x Ni _y Mn _z Mg _0.9-yz Fe _0.1 O ₂ , wherein 1≥x≥0.67 , 0.5≥y≥0.2, 0.7≥z≥0.3.

In the above scheme, although doping Mg can improve the performance, when Mg ²⁺ doping, although the cycle stability will be further improved, but the discharge specific capacity will also decrease with the increase of Mg ²⁺ doping amount. Small, especially P ₂ -Na _{2/ 3} Mn _0.8 Mg _0.2 O ₂ can only provide a discharge specific capacity of about 150mAh/g. However, P ₂ -Na _2/3 Mn _0.72 Mg _0.28 O ₂ showed a high reversible capacity of 220mAh/g. It is inferred that part of O ^2- participated in the electrochemical reaction and contributed part of the capacity. Similar behavior also exists in lithium-rich materials. However, its cycle stability is poor, and the capacity is only 150mAh/g after 30 cycles, which is far from meeting the application requirements.

Contents of the invention

The object of the present invention is to provide a kind of positive electrode material of layered sodium ion battery and its preparation method and application, the present invention doping appropriate amount of magnesium in the positive electrode material of sodium ion, not only can make trivalent manganese in the material fully oxidized into tetravalent manganese, At the same time, the reduction of Mn ⁴⁺ at low potential can be suppressed.

To achieve this purpose of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a layered sodium ion battery positive electrode material, the chemical formula of the layered sodium ion battery positive electrode material is Na _a Mg _{b Cux} Fe _{y Mnz} O ₂ , wherein, a+2x+3y +4z+2b=4 and 0.85≤a≤0.95, 0.05≤b≤0.1, x>0, y>0, z>0, and the valence of Mn is +4.

In the positive electrode material of the layered sodium ion battery described in the present invention, the valence of the transition metal element Mn is +4, and the use of low-priced Mg ²⁺ to replace Mn ³⁺ can reduce the high spin Mn ³⁺ formed due to charge compensation and alleviate the problem. Due to the Jahn-Teller effect, Mg ²⁺ doping can improve the kinetics of the O ₃ -P ₃ phase transition process, while inhibiting the reduction of Mn ⁴⁺ at low potentials. At the same time, Mg ²⁺ improves the Cu ³⁺ / The electrochemical activity of the Cu ²⁺ redox couple can increase the amount of deintercalation and average reaction potential of Na.

Preferably, the median particle diameter D50 of the layered sodium-ion battery positive electrode material is 5-15 μm, for example: 5 μm, 8 μm, 10 μm, 12 μm or 15 μm.

Preferably, the layered sodium ion battery cathode material is an O ₃ -type layered oxide cathode material.

In a second aspect, the present invention provides a method for preparing a positive electrode material for a layered sodium ion battery as described in the first aspect, the preparation method comprising the following steps:

(1) Copper source, iron source, manganese source and magnesium source are mixed with solvent to obtain mixed salt solution;

(2) adding the mixed salt solution, the precipitating agent and the complexing agent into the reaction vessel for reaction to obtain the precursor;

(3) heat treatment is performed after mixing the sodium source and the obtained precursor, and the layered sodium ion battery positive electrode material is obtained after rapid cooling.

In the preparation method of the present invention, for the layered oxide containing Mn, the cooling rate is accelerated after sintering, which helps to form a metastable phase containing more Mn ³⁺ and a higher interlayer sodium content, thereby improving the electrode material. reversible capacity.

Preferably, the copper source in step (1) includes any one or a combination of at least two of copper nitrate, copper acetate or copper sulfate.

Preferably, the iron source includes any one or a combination of at least two of ferric nitrate, ferric acetate, ferric citrate or ferrous sulfate.

Preferably, the manganese source includes any one or a combination of at least two of manganese acetate, manganese nitrate or manganese sulfate.

Preferably, the magnesium source includes any one or a combination of at least two of magnesium sulfate, magnesium chloride or magnesium nitrate.

Preferably, the total metal ion concentration of the mixed salt solution is 1.5-2 mol/L, for example: 1.5 mol/L, 1.6 mol/L, 1.7 mol/L, 1.8 mol/L, 1.9 mol/L or 2 mol/L wait.

Preferably, the precipitating agent comprises sodium hydroxide solution.

Preferably, the mass concentration of the precipitation agent is 30-34%, for example: 30%, 31%, 32%, 33% or 34%.

Preferably, the complexing agent includes ammonia water.

Preferably, the mass concentration of the complexing agent is 14-18%, for example: 14%, 15%, 16%, 17% or 18%.

Preferably, the reaction temperature in step (2) is 55-60°C, for example: 55°C, 56°C, 57°C, 58°C, 59°C or 60°C.

Preferably, the pH of the reaction is 10-10.5, for example: 10, 10.1, 10.2, 10.3, 10.4 or 10.5.

Preferably, nitrogen gas is introduced and stirred during the reaction.

Preferably, the stirring speed is 200-300rpm, for example: 200rpm, 220rpm, 250rpm, 280rpm or 300rpm and so on.

Preferably, blast drying is performed after the reaction.

Preferably, the mixed powder of the precursor and the sodium source is subjected to powder tableting treatment before the heat treatment in step (3).

Preferably, the sodium source includes any one or a combination of at least two of sodium carbonate, sodium nitrate, sodium acetate, sodium citrate or sodium carbonate.

Preferably, the heat treatment temperature is 800-900°C, for example: 800°C, 820°C, 850°C, 880°C or 900°C.

Preferably, the heat treatment time is 12-18 hours, for example: 12 hours, 13 hours, 15 hours, 16 hours or 18 hours.

In a third aspect, the present invention provides a positive electrode sheet, which includes the layered sodium ion battery positive electrode material as described in the first aspect.

In a fourth aspect, the present invention provides a sodium-ion battery, the sodium-ion battery comprising the positive electrode sheet as described in the third aspect.

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

(1) The present invention uses low-valent Mg ²⁺ instead of Mn ³⁺ to reduce the Jahn-Teller effect of Mn ³⁺ , and Mg ²⁺ doping can improve the kinetic performance of the O ₃ -P ₃ phase transition process while suppressing low potential Under the reduction of Mn ⁴⁺ , Mg ²⁺ improves the electrochemical activity of Cu ³⁺ /Cu ²⁺ redox couple, which can increase the amount of deintercalation and average reaction potential of Na.

(2) The Mg ²⁺ doping of the present invention can reduce the structural and volume changes of the crystal lattice, and suppress the occurrence of irreversible phase transitions. At the same time, the Mg ²⁺ doping can expand the interlayer distance, which not only contributes to the diffusion of Na ⁺ , but also improves the rate performance, and further alleviate the lattice strain caused by the extraction and intercalation of sodium.

(3) The reversible specific capacity of the battery in the first cycle of 0.2C can reach more than 114mAh/g, the capacity retention rate of 0.2C cycle for 200 cycles can reach more than 85%, and the capacity retention rate of 1C cycle for 500 cycles can reach 72%. % or more, the Na ⁺ reversible detachment and intercalation amount can reach more than 0.46.

Detailed ways

The technical solutions of the present invention will be further described below through specific embodiments. It should be clear to those skilled in the art that the embodiments are only for helping to understand the present invention, and should not be regarded as specific limitations on the present invention.

Example 1

This embodiment provides a layered sodium ion battery positive electrode material, the preparation method of the layered sodium ion battery positive electrode material is as follows:

(1) Mix CuSO ₄ , Fe ₂ (SO ₄ ) ₃ , Mn ₂ (SO ₄ ) ₃ and MgSO ₄ with deionized water at a molar ratio of Mg:Cu:Fe:Mn=0.08:0.22:0.3:0.4, Prepare the mixed salt solution whose total concentration of transition metal ions is 1.8mol/L, which is denoted as solution A, the preparation concentration is 32% NaOH solution as precipitant and denoted as solution B, and the preparation concentration is 15% ammonia water as complexing agent denoted as Solution C;

(2) Add solutions A, B, and C to the crystallization reactor respectively and keep overflowing. Dry at 60°C for 12 hours in an electric constant temperature blast drying oven to obtain the precursor;

(3) Press Na ₂ CO ₃ and precursor powder uniformly mixed in proportion to the powder, and after heat treatment in a muffle furnace at 850°C in an air atmosphere for 16 hours, accelerated cooling to obtain the layered sodium-ion battery positive electrode material , the chemical formula of the cathode material is Na _0.90 Mg _0.08 Cu _0.22 Fe _0.30 Mn _0.40 O ₂ .

Example 2

This embodiment provides a layered sodium ion battery positive electrode material, the preparation method of the layered sodium ion battery positive electrode material is as follows:

(1) CuSO ₄ , Fe ₂ (SO ₄ ) ₃ , Mn ₂ (SO ₄ ) ₃ and MgSO ₄ are mixed with deionized water according to the molar ratio of Mg:Cu:Fe:Mn=0.06:0.24:0.4:0.3, Prepare the mixed salt solution whose total concentration of transition metal ions is 1.85mol/L, which is denoted as solution A, the preparation concentration is 30% NaOH solution as precipitant and denoted as solution B, and the preparation concentration is 15% ammonia water as complexing agent denoted as Solution C;

(2) Add solutions A, B, and C to the crystallization reactor respectively and keep overflowing. Dry at 60°C for 12 hours in an electric constant temperature blast drying oven to obtain the precursor;

(3) Negatively mix Na ₂ CO ₃ and precursor powder in proportion to the powder tablet, and after heat treatment in a muffle furnace at 880°C in an air atmosphere for 16 hours, accelerated cooling to obtain the layered sodium-ion battery positive electrode material , the chemical formula of the cathode material is Na _0.92 Mg _0.06 Cu _0.24 Fe _0.4 Mn _0.3 O ₂ .

Example 3

The only difference between this embodiment and embodiment 1 is that the molar ratio of magnesium ions in the material is controlled to be 0.03 (ie b=0.03), and other conditions and parameters are exactly the same as those of embodiment 1.

Example 4

The only difference between this embodiment and embodiment 1 is that the molar ratio of magnesium ions in the material is controlled to be 0.12 (ie b=0.12), and other conditions and parameters are exactly the same as those of embodiment 1.

Example 5

The only difference between this embodiment and embodiment 1 is that the heat treatment temperature in step (3) is 750° C., and other conditions and parameters are exactly the same as those in embodiment 1.

Example 6

The only difference between this embodiment and embodiment 1 is that the heat treatment temperature in step (3) is 950° C., and other conditions and parameters are exactly the same as those in embodiment 1.

Comparative example 1

The only difference between this comparative example and Example 1 is that no magnesium is added, other conditions and parameters are exactly the same as those of Example 1, and the chemical formula of the positive electrode material is Na _0.90 Cu _0.22 Fe _0.30 Mn _0.48 O ₂ .

Performance Testing:

The sodium ion positive electrode material that obtains with embodiment 1-6 and comparative example 1 is positive electrode active material, and metal sodium is negative electrode, and glass fiber film is as separator, and the NaClO ₄ /EC/DMC/PC of 1M is electrolyte solution in argon glove box Assembled into a CR2032 button cell. Among them, the positive pole piece is the active material, acetylene black and PVDF dissolved in NMP are evenly mixed according to the mass ratio of 70:20:10, then coated on the aluminum foil, then cut into 8×8mm ² size pole pieces, and placed at 110°C 10h in a vacuum oven. Place the assembled button battery on the LAND for constant current charge and discharge test. The test results are shown in Table 1:

Table 1

As can be seen from Table 1, it can be obtained from Examples 1-2 that the reversible specific capacity of the battery in the first cycle at 0.2C can reach more than 114mAh/g, and the capacity retention rate after 200 cycles at 0.2C can reach 85%. % or more, the capacity retention rate of 1C cycle 500 cycles can reach more than 72%, and the reversible Na ⁺ detachment and intercalation amount can reach more than 0.46.

From the comparison of Example 1 and Examples 3-4, it can be obtained that in the layered sodium ion battery positive electrode material of the present invention, the doping amount of magnesium will affect its performance, and the doping amount of magnesium is controlled at 0.05～0.1, so The performance of the positive electrode material of the layered sodium-ion battery is good. If the doping amount of magnesium is too high, the capacity of the material will decrease significantly, resulting in a decrease in material performance. The valent manganese is completely oxidized to tetravalent manganese, resulting in the Jahn-Teller effect of Mn ³⁺ .

From the comparison of Example 1 and Examples 5-6, it can be seen that in the preparation process of the layered sodium ion battery cathode material of the present invention, the temperature of heat treatment will affect its performance, and the temperature of heat treatment is controlled at 800-900 ° C to obtain The performance of layered sodium-ion battery cathode material is good. If the temperature of heat treatment is too high, the degree of oxidation of the material is too high, resulting in cracks in the material and a decrease in its safety performance. If the temperature of heat treatment is too low, trivalent manganese cannot be completely oxidized into Tetravalent manganese, causing the Jahn-Teller effect of Mn ³⁺ to occur.

From the comparison of Example 1 and Comparative Example 1, it can be concluded that the use of low-priced Mg ²⁺ to replace Mn ³⁺ in the present invention can reduce the Jahn-Teller effect of Mn ³⁺ , and Mg ²⁺ doping can improve the O ₃ -P ₃ phase transition process Kinetic performance, while inhibiting the reduction of Mn ^{4 +} at low potential, while Mg ²⁺ improves the electrochemical activity of the Cu ³⁺ /Cu ²⁺ redox couple, which can increase the amount of deintercalation and average reaction potential of Na .

Mg ²⁺ doping affects the crystal structure and electrochemical performance of O ₃ -Na _0.90 Mg _0.08 Cu _0.22 Fe _0.30 Mn _0.40 O ₂ . In the voltage range of 2.4–3.9 V, O ₃ -Na _0.90 Mg _0.08 Cu _0.22 Fe _0.30 Mn _0.40 O ₂ corresponds to 0.42 Na ⁺ reversible extraction and intercalation while O ₃ -Na _0.90 Cu _0.22 Fe _0.30 Mn _0.48 O ₂ corresponds to 0.32 Na ⁺ reversible out and in. In the voltage range of 2.4-4.0V, O ₃ -Na _0.90 Mg _0.08 Cu _0.22 Fe _0.30 Mn _0.40 O ₂ has a reversible specific capacity of 116mAh/g, corresponding to 0.465 Na ⁺ reversible extraction and insertion; while O ₃ -Na _0.90 Cu The reversible specific capacity of _0.22 Fe _0.30 Mn _0.48 O ₂ is only 90mAh/g, corresponding to 0.36 Na ⁺ reversible extraction and intercalation.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, and those skilled in the art should understand that any person skilled in the art should be aware of any disclosure in the present invention Within the technical scope, easily conceivable changes or substitutions all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. A layered sodium ion battery positive electrode material, characterized in that, the chemical formula of the layered sodium ion battery positive electrode material is Na _a Mg _b Cu _x Fe _y Mn _z O ₂ , wherein, a+2x+3y+4z +2b=4 and 0.85≤a≤0.95, 0.05≤b≤0.1, x>0, y>0, z>0, the valence of Mn is +4. 2 . The layered sodium ion battery positive electrode material according to claim 1 , wherein the median particle size D50 of the layered sodium ion battery positive electrode material is 5-15 μm. 3 . 3. layered sodium-ion battery positive electrode material as claimed in claim 1 or 2, is characterized in that, described layered sodium-ion battery positive electrode material is O ₃ type layered oxide positive electrode material. 4. A preparation method of layered sodium-ion battery positive electrode material as described in any one of claims 1-3, is characterized in that, described preparation method comprises the following steps: (1) Copper source, iron source, manganese source and magnesium source are mixed with solvent to obtain mixed salt solution; (2) adding the mixed salt solution, the precipitating agent and the complexing agent into the reaction vessel for reaction to obtain the precursor; (3) heat treatment is performed after mixing the sodium source and the obtained precursor, and the layered sodium ion battery positive electrode material is obtained after rapid cooling. 5. preparation method as claimed in claim 4, is characterized in that, step (1) described copper source comprises any one or the combination of at least two in copper nitrate, copper acetate or copper sulfate; Preferably, the iron source includes any one or a combination of at least two of ferric nitrate, ferric acetate, ferric citrate or ferrous sulfate; Preferably, the manganese source includes any one or a combination of at least two of manganese acetate, manganese nitrate or manganese sulfate; Preferably, the magnesium source includes any one or a combination of at least two of magnesium sulfate, magnesium chloride or magnesium nitrate; Preferably, the total metal ion concentration of the mixed salt solution is 1.5-2 mol/L. 6. the preparation method as claimed in claim 4 or 5, is characterized in that, the precipitation agent described in step (2) comprises sodium hydroxide solution; Preferably, the mass concentration of the precipitating agent is 30-34%; Preferably, the complexing agent includes ammonia; Preferably, the mass concentration of the complexing agent is 14-18%. 7. The preparation method according to any one of claims 4-6, characterized in that the reaction temperature in step (2) is 55-60°C; Preferably, the pH of the reaction is 10-10.5; Preferably, feed nitrogen and stir during the reaction; Preferably, the stirring speed is 200-300rpm; Preferably, blast drying is performed after the reaction. 8. The preparation method according to any one of claims 4-7, wherein, before the heat treatment in step (3), the mixed powder of the precursor and the sodium source is subjected to powder compression treatment; Preferably, the sodium source comprises any one or a combination of at least two of sodium carbonate, sodium nitrate, sodium acetate, sodium citrate or sodium carbonate; Preferably, the temperature of the heat treatment is 800-900°C; Preferably, the heat treatment time is 12-18 hours. 9. A positive electrode sheet, characterized in that the positive electrode sheet comprises the layered sodium ion battery positive electrode material according to any one of claims 1-3. 10. A sodium-ion battery, characterized in that the sodium-ion battery comprises the positive electrode sheet according to claim 9.