A sodium ion battery negative electrode material with a porous structure phosphorus cobalt alloy and a preparation method thereof

Abstract

The application relates to a preparation method of a porous structure phosphorus-cobalt alloy negative electrode material for a sodium ion battery, wherein the phosphorus-cobalt alloy is in a porous structure, the particle diameter is within 20 microns, and the pore diameter is within 5 microns. The preparation method is that after ball milling, heating and heat preservation are carried out in a nitrogen or argon atmosphere, so that the target product is obtained. The phosphorus-cobalt alloy with small particle diameter and porous characteristics is prepared through high-energy ball milling and heat carbon reduction, the small particle diameter is beneficial to the rapid entry and discharge of sodium ions, the large-current charging and discharging capacity is improved, and the porous structure is beneficial to providing more sodium intercalation gap positions, and the sodium storage capacity is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of negative electrode materials for batteries, and more specifically, to a porous phosphorus-cobalt alloy negative electrode material for sodium-ion batteries and its preparation method. Background Technology

[0002] Because the radius of sodium ions is much larger than that of lithium ions, commercially available carbon anode materials for lithium-ion batteries cannot be used in sodium-ion batteries. Phosphorus-based alloy anodes have high specific capacity, but exhibit poor cycle stability due to significant volume expansion during sodium insertion / extraction. Furthermore, phosphorus's poor conductivity makes it difficult to achieve high-current charge / discharge. Moreover, due to phosphorus's high reactivity, it is easily oxidized during alloy preparation, leading to incomplete and uneven reactions in the synthesis of related phosphorus-based alloys. Summary of the Invention

[0003] The purpose of this invention is to provide a porous phosphorus-cobalt alloy anode material for sodium-ion batteries and its preparation method. By alloying, the conductivity of phosphorus is improved. By constructing a porous structure, a series of problems such as poor cycle performance and low reversible capacity of phosphorus-based anodes are solved. The introduced porous structure also reserves expansion space for the possible volume expansion of phosphorus-based alloys, which is beneficial to improving cycle stability and overcoming the shortcomings of the prior art.

[0004] The technical solution of this invention to solve its technical problem is: a method for preparing a porous phosphorus-cobalt alloy anode material for sodium-ion batteries, characterized by comprising the following steps:

[0005] S1) Weigh cobalt oxide and carbon powder according to a molar ratio of 1:2. The cobalt oxide is of analytical grade, and the carbon powder has a purity of 99.99% and a particle size of less than 20μm. Pour them into a ball mill, add anhydrous ethanol, and ball mill at 300-400 rpm for 2-5 hours. Weigh red phosphorus powder according to a molar ratio of cobalt oxide to red phosphorus of 1:1 to 1:3, and continue to pour it into the ball mill with the above slurry and continue to ball mill for 2-5 hours. After taking it out, vacuum dry or spray dry it for later use to form semi-finished product A.

[0006] S2) Place semi-finished product A into an atmosphere furnace and heat it to 400-600°C at 2-5°C / min under a nitrogen or argon atmosphere. Hold the temperature for 2-6 hours, then continue heating at 2-5°C / min to 700-1100°C and hold for 2-6 hours to obtain the target product.

[0007] In the above-mentioned method for preparing a porous phosphorus-cobalt alloy anode material for sodium-ion batteries, the solid content of anhydrous ethanol is 40% to 70%, and the grinding balls are 5mm zirconia balls.

[0008] In the above-mentioned method for preparing a porous phosphorus-cobalt alloy anode material for sodium-ion batteries, the purity of the red phosphorus powder is not less than 99%.

[0009] A porous phosphorus-cobalt alloy anode material for sodium-ion batteries is prepared according to the above-mentioned preparation method, wherein the phosphorus-cobalt alloy has a porous structure with a particle diameter of less than 20 μm and a pore size of less than 5 μm.

[0010] The beneficial effects of this invention are:

[0011] 1) A phosphorus-cobalt alloy with small particle size and porous characteristics was prepared by high-energy ball milling combined with thermal carbon reduction. The small particle size is conducive to the rapid entry and exit of sodium ions, which is beneficial to the improvement of high current charging and discharging capabilities. The porous structure is conducive to providing more interstitial sites for sodium, effectively improving the sodium storage capacity.

[0012] 2) Cobalt oxide is reduced to cobalt, which immediately participates in the alloying reaction of phosphorus under high temperature conditions. This can effectively improve the purity of cobalt-phosphorus alloys, ensure the efficient utilization of cobalt, and reduce the cost waste caused by cobalt not participating in the alloying of cobalt-phosphorus alloys.

[0013] 3) The prepared porous structure provides space for the possible volume expansion of the phosphorus-cobalt alloy, which is beneficial to improving cycle stability. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a diagram of a hard carbon anode material with a multilayer core-shell structure obtained using Embodiment 1 of the present invention;

[0016] Figure 2 This is a diagram of a hard carbon anode material with a multilayer core-shell structure obtained using Embodiment 2 of the present invention;

[0017] Figure 3 This is a diagram of a hard carbon anode material with a multilayer core-shell structure obtained using Embodiment 3 of the present invention;

[0018] Figure 4 This is a chart showing the charge and discharge specific capacity test values ​​of the negative electrode material in Example 1;

[0019] Figure 5 This is a chart showing the charge and discharge specific capacity test values ​​of the negative electrode material in Example 2;

[0020] Figure 6This is a chart showing the charge and discharge specific capacity test values ​​of the negative electrode material in Example 3;

[0021] Figure 4-6 In the table, the horizontal axis represents the cycle number, and the vertical axis represents the charge / discharge specific capacity. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] Example 1

[0024] This invention discloses a method for preparing a porous cobalt phosphorus alloy anode material for sodium-ion batteries, the steps of which are as follows:

[0025] 1) Weigh cobalt oxide and carbon powder according to a molar ratio of 1:2, pour them into a ball mill, add anhydrous ethanol, and the solid content is 50%. Ball mill at 200 rpm for 2 hours using 5 mm zirconia balls. Weigh red phosphorus powder (purity not less than 99%) according to a cobalt oxide:red phosphorus molar ratio of 1:3, and continue to pour it into the ball mill with the above slurry. Continue to ball mill for 2 hours, remove and vacuum dry for later use to form semi-finished product A.

[0026] (2) Place semi-finished product A into an atmosphere furnace and heat it to 400°C at 2°C / min under an argon atmosphere. Hold it for 2 hours and continue heating it to 900°C at 2°C / min. Hold it for 2 hours to obtain the target product.

[0027] The obtained negative electrode material, such as Figure 1 As shown.

[0028] Figure 4 This is a diagram showing the charge and discharge specific capacity of the obtained negative electrode material.

[0029] Example 2

[0030] The preparation steps of a porous cobalt-phosphorus alloy anode material for sodium-ion batteries are as follows:

[0031] 1) Weigh cobalt oxide and carbon powder according to a molar ratio of 1:2. The cobalt oxide is analytical grade, and the carbon powder has a purity of 99.99% and a particle size of less than 20 μm. Pour them into a ball mill, add anhydrous ethanol (70% solid content), and ball mill at 400 rpm for 5 hours. The ball milling balls are 5 mm zirconia balls. Weigh red phosphorus powder (purity not less than 99%) according to a cobalt oxide:red phosphorus molar ratio of 1:2, and continue to pour it into the ball mill with the above slurry. Continue to ball mill for 5 hours. After removal, spray dry for later use to form semi-finished product A.

[0032] (2) Place semi-finished product A into an atmosphere furnace and heat it to 600°C at 5°C / min under a nitrogen atmosphere. Hold it for 6 hours and continue heating it to 1100°C at 5°C / min. Hold it for 6 hours to obtain the target product.

[0033] The obtained negative electrode material, such as Figure 2 As shown.

[0034] Figure 5 This is a diagram showing the charge and discharge specific capacity of the obtained negative electrode material.

[0035] Example 3

[0036] The preparation steps of a porous cobalt-phosphorus alloy anode material for sodium-ion batteries are as follows:

[0037] 1) Weigh cobalt oxide and carbon powder according to a molar ratio of 1:2. The cobalt oxide is analytical grade, and the carbon powder has a purity of 99.99% and a particle size of less than 20 μm. Pour them into a ball mill, add anhydrous ethanol, and ball mill at 300 rpm for 3 hours. The ball milling balls are 5 mm zirconium oxide balls. Weigh red phosphorus powder (purity not less than 99%) according to a cobalt oxide:red phosphorus molar ratio of 1:1, and continue to pour it into the ball mill with the above slurry. Continue to ball mill for 3 hours. After removal, vacuum dry or spray dry for later use to form semi-finished product A.

[0038] (2) Place semi-finished product A into an atmosphere furnace and heat it to 500°C at 3°C / min under a nitrogen or argon atmosphere. Hold it at this temperature for 4 hours, and then continue heating it to 1000°C at 3°C / min. Hold it at this temperature for 4 hours to obtain the target product.

[0039] The obtained negative electrode material, such as Figure 3 As shown.

[0040] Figure 6 This is a diagram showing the charge and discharge specific capacity of the negative electrode material.

[0041] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a porous phosphorus-cobalt alloy anode material for sodium-ion batteries, characterized in that... Includes the following steps: S1) Weigh cobalt oxide and carbon powder according to a molar ratio of 1:

2. The cobalt oxide is of analytical grade, and the carbon powder has a purity of 99.99% and a particle size of less than 20μm. Pour them into a ball mill, add anhydrous ethanol, and ball mill at 300-400 rpm for 2-5 hours to obtain a slurry. Weigh red phosphorus powder according to a molar ratio of cobalt oxide to red phosphorus of 1:1 to 1:3, and continue to pour it into the ball mill and ball mill it with the slurry for another 2-5 hours. After removing it, vacuum dry or spray dry it for later use to form semi-finished product A. S2) Place semi-finished product A into an atmosphere furnace and heat it to 400-600°C at 2-5°C / min under a nitrogen or argon atmosphere. Hold the temperature for 2-6 hours, then continue heating at 2-5°C / min to 700-1100°C and hold for 2-6 hours to obtain the target product.

2. The method for preparing a porous phosphorus-cobalt alloy anode material for sodium-ion batteries according to claim 1, characterized in that: The purity of the red phosphorus powder is not less than 99%.

3. A porous phosphorus-cobalt alloy anode material for sodium-ion batteries, characterized in that: The phosphorus-cobalt alloy is prepared according to the method described in claim 1, wherein the phosphorus-cobalt alloy has a porous structure with a particle diameter of less than 20 μm and a pore size of less than 5 μm.

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