Layered structure phosphorus iron negative electrode material for lithium ion battery and preparation method thereof

Abstract

The present application relates to a kind of layered structure phosphorus iron negative electrode material for lithium ion battery and preparation method, and the phosphorus iron alloy of phosphorus iron negative electrode material is multilayer block structure, particle diameter is 10-20 μm, single layer thickness is less than 100 nm, material does not require layer number, allow single layer not to grow complete.The negative electrode material of the present application is processed by ball milling process, ball milling reduces the particle size of iron oxide, then carbon powder is used to reduce iron oxide, reduce the particle size of iron, shorten the path of lithium ion transport, and improve the large current discharge capacity.At the same time, carbon powder reduces iron oxide and iron and phosphorus form alloy in the same heat treatment process, greatly shorten the preparation time and cost, simple and controllable preparation of phosphorus iron alloy.

Description

Technical Field

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

[0002] Battery life has become a major point of criticism for lithium-ion batteries. The root cause is that the capacity of commercially available carbon anode materials has approached their theoretical limit (372 mAh / g), necessitating the development of new lithium-ion battery anode materials with high capacity and long lifespan. Phosphorus-based alloys are highly favored due to their theoretical specific capacity of 2596 mAh / g. However, phosphorus's near-non-conductive nature hinders lithium-ion transport within them, and its high reactivity impedes their synthesis and development, preventing their commercialization. Currently, the synthesis of phosphorus-based alloys mainly involves ball milling or high-temperature reaction of phosphorus powder with metal powder. Due to phosphorus's high reactivity, the processing conditions are demanding, resulting in low efficiency and significant safety hazards. The prepared alloys suffer from incomplete and uneven reactions, leading to poor capacity performance and cycle life in the resulting phosphorus-based alloy samples. Summary of the Invention

[0003] The purpose of this invention is to provide a layered phosphorus-iron anode material for lithium-ion batteries and its preparation method, which solves the problems of insufficient reaction and safety hazards of conventional phosphorus-iron alloys. By preparing the alloy, the conductivity of phosphorus is effectively improved, and a layered phosphorus-iron alloy anode material is prepared, realizing the controllable preparation of high-capacity and long-life phosphorus-iron anode materials 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 layered phosphorus-iron anode material for lithium-ion batteries, characterized by comprising the following steps:

[0005] S1) Weigh iron oxide and carbon powder according to a molar ratio of 1:2. The iron 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 iron 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 900-1100°C and hold for 2-6 hours to obtain the target product.

[0007] In the above-mentioned preparation method of layered phosphorus iron anode material for lithium-ion batteries, the solid content of anhydrous ethanol is 40%~70%, and the milling ball is a 5mm zirconium oxide ball.

[0008] In the above-mentioned preparation method of layered phosphorus iron anode material for lithium-ion batteries, the purity of red phosphorus powder is not less than 99%.

[0009] A layered phosphorus-iron anode material for lithium-ion batteries is prepared according to the above-mentioned preparation method. The phosphorus-iron alloy has a multi-layered block structure with a particle diameter of 10~20 µm and a single layer thickness of less than 100 nm. There are no requirements on the number of layers, and it is permissible for a single layer not to be fully grown.

[0010] The beneficial effects of this invention are:

[0011] 1) Ball milling reduces the particle size of iron oxide, and then carbon powder is used to reduce the iron particle size, shorten the lithium ion transport path, and facilitate the improvement of high current discharge capability.

[0012] 2) The reduction of iron oxide by carbon powder and the formation of iron-phosphorus alloy are completed in the same heat treatment process, which greatly shortens the preparation time and cost, and makes it easy and controllable to prepare ferrophosphorus alloys.

[0013] 3) Strictly controlling the process parameters of carbon powder reduction of iron oxide can controllably prepare phosphorus-iron alloy with a layered structure, which is conducive to the reversible insertion and extraction of lithium ions and improves the cycle stability of the anode material.

[0014] 4) The layered structure provides space for the possible volume expansion of the phosphorus-iron alloy, which is beneficial to improving cycle stability. Attached Figure Description

[0015] 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.

[0016] Figure 1 This is a product material drawing obtained using Embodiment 1 of the present invention;

[0017] Figure 2 This is a product material drawing obtained using Embodiment 2 of the present invention;

[0018] Figure 3 This is a product material drawing obtained using Embodiment 3 of the present invention;

[0019] Figure 4This is a chart showing the charge and discharge specific capacity test values ​​of the negative electrode material in Example 1;

[0020] Figure 5 This is a chart showing the charge and discharge specific capacity test values ​​of the negative electrode material in Example 2;

[0021] Figure 6 This is a chart showing the charge and discharge specific capacity test values ​​of the negative electrode material in Example 3;

[0022] 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

[0023] 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. Example

[0024] This invention discloses a method for preparing a layered phosphorus-iron anode material for lithium-ion batteries, the steps of which are as follows:

[0025] 1) Weigh iron 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 5mm zirconia balls. Weigh red phosphorus powder (purity not less than 99%) according to a molar ratio of iron oxide to red phosphorus 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 the temperature for 2 hours, then continue heating it to 900°C at 2°C / min and 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. Example

[0029] The preparation steps for layered iron-phosphorus anode material used in lithium-ion batteries are as follows:

[0030] 1) Weigh iron oxide and carbon powder according to a molar ratio of 1:2. The iron oxide is 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 (70% solid content), and ball mill at 400 rpm for 5 hours. Use 5mm zirconia balls for milling. Weigh red phosphorus powder (purity not less than 99%) according to a molar ratio of iron oxide to red phosphorus 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.

[0031] 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 the temperature for 6 hours, then continue heating it to 1100°C at 5°C / min and hold it for 6 hours to obtain the target product.

[0032] The obtained negative electrode material, such as Figure 2 As shown.

[0033] Figure 5 This is a diagram showing the charge and discharge specific capacity of the obtained negative electrode material. Example

[0034] The preparation steps for layered iron-phosphorus anode material used in lithium-ion batteries are as follows:

[0035] 1) Weigh iron oxide and carbon powder according to a molar ratio of 1:2. The iron oxide is 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 rpm for 3 hours. The ball milling balls are 5mm zirconia balls. Weigh red phosphorus powder (purity not less than 99%) according to a molar ratio of iron oxide to red phosphorus of 1:1. Continue to pour it into the ball mill and ball mill it with the above slurry for another 3 hours. After removal, vacuum dry or spray dry for later use to form semi-finished product A.

[0036] 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 the temperature for 4 hours, then continue heating it to 1000°C at 3°C / min and hold it for 4 hours to obtain the target product.

[0037] The obtained negative electrode material, such as Figure 3 As shown.

[0038] Figure 6 This is a diagram showing the charge and discharge specific capacity of the negative electrode material.

[0039] 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 layered phosphorus-iron anode material for lithium-ion batteries, characterized in that... Includes the following steps: S1) Weigh iron oxide and carbon powder according to a molar ratio of 1:

2. The iron 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 300-400 rpm for 2-5 hours to obtain a slurry. Weigh red phosphorus powder according to a molar ratio of iron oxide to red phosphorus of 1:1 to 1:3, and continue to pour it into the ball mill with the above slurry for 2-5 hours. After removal, vacuum dry or spray dry for later use to form semi-finished product A. S2) Place semi-finished product A in an atmosphere furnace and heat it to 400-600℃ at 2-5℃ / min under a nitrogen or argon atmosphere. Hold it at this temperature for 2-6 hours, and continue to heat it to 900-1100℃ at 2-5℃ / min. Hold it at this temperature for 2-6 hours to obtain the target product, ferrophosphorus alloy. The ferrophosphorus alloy has a multi-layer block structure with a single layer thickness of less than 100 nm.

2. The method for preparing the layered phosphorus-iron anode material for lithium-ion batteries according to claim 1, characterized in that: The grinding balls are 5mm zirconia balls.

3. The method for preparing the layered phosphorus-iron anode material for lithium-ion batteries according to claim 1, characterized in that: The purity of the red phosphorus powder is not less than 99%.

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