Battery anode materials, their preparation methods and applications

Abstract

This invention discloses a battery anode material, its preparation method, and its application. The preparation method includes the following steps: 1) preparing a carbon nanotube slurry; 2) coating: coating the carbon nanotube slurry onto the surface of a substrate; 3) freeze-drying: the coating / substrate continuously advances into a liquid ammonia freeze-drying tank, and then into a low-temperature drying chamber to obtain an aerogel carbon nanotube coating / substrate; 4) pre-metallization: the aerogel carbon nanotube coating / substrate continues to advance into a blue liquid ammonia solution of metals Li, Na, or K, saturating the aerogel with this blue solution, and then enters an evaporation chamber to evaporate the ammonia, obtaining a three-dimensional anode material pre-embedded with elemental lithium, sodium, and potassium. This anode material has a three-dimensional porous structure, is sponge-like and elastic, and can rebound to its original shape after compression, which is beneficial for the storage and transport of lithium, sodium, or potassium ions. When used as a battery anode, it exhibits good electrochemical performance, high and stable ion storage efficiency. The preparation process of this invention is simple and has broad commercial application prospects.

Description

Technical Field

[0001] This invention belongs to the field of battery material processing technology, specifically relating to a battery negative electrode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are the dominant force in the battery industry today, developing rapidly and driving revolutionary advancements in many fields, including smartphones, laptops, and electric vehicles. However, lithium is a relatively scarce element, with an abundance of only 0.0017% in the Earth's crust. Therefore, the search has been ongoing for a new rechargeable battery to replace lithium batteries. Sodium and potassium are thousands of times more abundant than lithium in the Earth's crust, and their properties are similar to lithium. Sodium-ion and potassium-ion batteries share a similar "rocking chair" charging and discharging principle with lithium-ion batteries, and are therefore considered promising candidates.

[0003] Graphite, a commonly used anode material in lithium-ion batteries, is unsuitable for sodium / potassium-ion batteries because the large diameter of sodium / potassium ions prevents them from intercalating and deintercalating within the graphite layers. Furthermore, sodium / potassium ions cannot form a stable phase structure with graphite. Other anode materials for sodium / potassium-ion batteries have also been studied concurrently, including graphitized hard carbon, alloys, oxides, and organic composites. However, most current anode materials experience significant volume expansion during sodium / potassium ion intercalation, leading to irreversible capacity decay.

[0004] The present invention is made to address the aforementioned problems existing in the prior art. Summary of the Invention

[0005] To address at least one of the aforementioned technical problems, the present invention aims to provide a battery anode material, its preparation method, and its application. The preparation method utilizes freeze-drying technology to prepare a three-dimensional porous carbon nanotube aerogel material, which is then impregnated with a liquid ammonia solution that adsorbs alkali metals, followed by evaporation to remove the ammonia, thereby obtaining a three-dimensional anode material with pre-implanted metal seeds, high elasticity, good conductivity, and high metal storage efficiency.

[0006] The technical solution of this invention is as follows:

[0007] This invention provides a method for preparing a battery negative electrode material, comprising the following steps:

[0008] Step 1, Preparation of carbon nanotube slurry: Disperse carbon nanotubes in a solvent, add a certain amount of binder and stabilizer, and stir continuously at a speed of 200-300 rpm for 20-30 minutes to make it fully mixed and uniform, thus obtaining the carbon nanotube slurry;

[0009] Step 2, Coating: The above carbon nanotube slurry is coated onto the surface of the substrate;

[0010] Step 3, freeze drying: The above coating / substrate is continuously advanced into the liquid ammonia freeze dehydration tank, and then into the low temperature drying chamber to obtain the aerogel carbon nanotube coating / substrate;

[0011] Step 4, Pre-metallization: The aerogel carbon nanotube coating / substrate continues to advance and enters a blue liquid ammonia solution of metals Li, Na, or K, so that the aerogel is filled with this blue solution. Then it enters the evaporation chamber to evaporate the ammonia, thus obtaining a three-dimensional negative electrode material with pre-embedded lithium, sodium, or potassium elements.

[0012] Preferably, in step one, the carbon nanotube is at least one of single-walled carbon nanotube or multi-walled carbon nanotube;

[0013] The carbon nanotubes have a purity greater than 99%, a diameter of 10–200 nm, and a length of 5–20 μm.

[0014] Preferably, in step one, the concentration of the prepared carbon nanotube slurry is 10% to 15%, and the mass ratio of carbon nanotubes to binder and stabilizer is 20 to 10:0.7:0.3.

[0015] Preferably, in step one, the solvent is at least one selected from deionized water, alcohol, ethylene glycol, propanol, isopropanol, acetone, and N-methylpyrrolidone.

[0016] In step one, the adhesive is polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), or alginate (Li). + Na + K + Salt), pectin (Li + Na + K + At least one of the following: salts;

[0017] In step one, the stabilizer is sodium carboxymethyl cellulose (CMC).

[0018] Preferably, in step two, the substrate is a copper substrate, which is a copper foil or a copper mesh, and the blue solution in step four is a blue liquid ammonia solution of metallic Li.

[0019] Preferably, in step two, the substrate is an aluminum substrate, which is an aluminum foil or an aluminum mesh, and the blue solution in step four is a blue liquid ammonia solution of metallic Na or K.

[0020] Preferably, in step three, the temperature range of the low-temperature drying chamber is controlled between -33℃ and 0℃.

[0021] Preferably, in step four, the concentration of the blue liquid ammonia solution is 0.5–1.5 mol / L.

[0022] In the preparation method of battery anode materials, carbon nanotube slurry is first coated onto a current collector (copper / aluminum substrate), and then freeze-dried to ensure the aerogel state of the carbon nanotube coating, resulting in a sponge-like three-dimensional porous carbon nanotube aerogel coating. Subsequently, the aerogel carbon nanotube coating / substrate is further introduced into a liquid ammonia blue solution containing Li, Na, or K metals, allowing the aerogel to absorb the blue solution. It then enters an evaporation chamber to evaporate the ammonia, yielding a three-dimensional anode material pre-embedded with lithium, sodium, and potassium elements. By controlling the concentration of the blue liquid ammonia solution, the amount of metal seeds embedded in the anode material is controlled. The presence of metal seeds effectively guides the electroplating of lithium (sodium or potassium), preventing random nucleation and growth of metal on the anode surface, thus avoiding problems such as uneven lithium (sodium or potassium) plating and metal dendrite formation.

[0023] This invention also provides the battery anode material prepared by the above-mentioned preparation method and its application in the manufacture of lithium / sodium / potassium ion batteries. The battery anode material can be used as the anode of lithium, sodium or potassium ion batteries, and has good electrochemical performance, high metal storage efficiency and stability. Specifically, copper is used as the substrate for lithium ion batteries, and aluminum is used as the substrate for sodium / potassium ion batteries.

[0024] The beneficial effects of this invention are:

[0025] 1) The preparation method of this invention is simple, the product has good consistency, strong operability, and is conducive to industrial production. It also has broad commercial application prospects. The three-dimensional porous structure of the material is extremely elastic, which can control the volume change of the negative electrode within 10%, greatly alleviate the huge volume expansion during charging and discharging, effectively improve the cycle performance of the battery, reduce the polarization of the battery, and successfully suppress the generation of lithium (sodium or potassium) dendrites.

[0026] 2) This invention first uses freeze-drying technology to prepare three-dimensional porous carbon nanotube aerogel material, then impregnates it with liquid ammonia solution that adsorbs alkali metals, and then evaporates to remove the ammonia to pre-embed lithium, sodium and potassium elements inside the carbon nanotube aerogel, so that the metal elements are uniformly adsorbed in the carbon nanotube aerogel, which can effectively increase the contact area between the metal elements and the electrolyte, reduce the current density, and thus make the metal ion distribution more uniform, so as to avoid the formation of metal dendrites.

[0027] 3) The pre-implanted metal seed crystals can effectively guide the electroplating of lithium (sodium or potassium) metal, avoiding random nucleation and growth of metal on the negative electrode surface, thereby avoiding problems such as uneven lithium (sodium or potassium) plating on the negative electrode and the generation of metal dendrites.

[0028] 4) The electrochemically active material prepared by this invention has good conductivity, large interlayer spacing, and high metal storage efficiency, making it suitable for use in lithium (sodium or potassium) ion batteries. When this material is used as the negative electrode of a battery, the resulting battery has the advantages of high capacity and good rate performance. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0030] Figure 1 This is a SEM image of the surface of the carbon nanotube aerogel sample prepared in Example 1 of the present invention;

[0031] Figure 2 This is a SEM image of the cross-section of the carbon nanotube aerogel sample prepared in Example 1 of the present invention;

[0032] Figure 3 This is a high-magnification SEM image of the battery negative electrode material prepared in Example 1 of the present invention;

[0033] Figure 4 The cycling performance and coulombic efficiency curves of the sodium-ion battery prepared from the sample in Example 1 of this invention are shown. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0035] Example 1

[0036] Add 10 kg of carbon nanotubes (Suzhou First Element, CNTp, the same below) to 90 kg of 40% alcohol solution. After ultrasonic treatment, add 7 kg of 10% sodium pectate solution and 3 kg of 10% sodium carboxymethyl cellulose solution to the mixture. Stir continuously at a speed of 200 rpm for 30 min to make it fully mixed and uniform, and the carbon nanotube slurry is obtained.

[0037] The carbon nanotube slurry was coated onto the surface of aluminum foil, then fed into a liquid ammonia freezing dehydration tank via a transmission machine, and then entered a -10℃ low temperature drying chamber to obtain an aerogel carbon nanotube coating / aluminum material.

[0038] The aerogel carbon nanotube coating / substrate continues to move forward and enters a 1 mol / L metallic sodium blue liquid ammonia solution, so that the aerogel is filled with this blue solution. Then it enters the evaporation chamber to evaporate the ammonia, thus obtaining a three-dimensional negative electrode material with embedded sodium.

[0039] The carbon nanotube aerogel sample obtained in this embodiment has a thickness of 30 μm and an areal density of 19.5 g / m³. 2 With a porosity of 70%, its surface and cross-sectional SEM images are as follows: Figure 1 and 2As shown in the image, the sample clearly exhibits a sponge-like three-dimensional porous structure with pore sizes ranging from nanometers to micrometers. It possesses good elasticity and a large specific surface area, effectively increasing the contact area between metallic sodium and the electrolyte, reducing current density, and thus resulting in a more uniform distribution of sodium ions, successfully preventing the formation of sodium dendrites. The resulting battery anode material maintains a relatively constant thickness and has an areal density of 20.1 g / m³. 2 With a porosity of 68%, its high-magnification SEM image is as follows: Figure 3 As shown, sodium crystals are uniformly distributed on the surface of carbon nanotubes, which can effectively guide sodium electroplating and prevent sodium from randomly nucleating and growing on the negative electrode surface, thereby avoiding problems such as uneven sodium plating on the negative electrode and the formation of sodium dendrites.

[0040] Using a sodium metal sheet as the counter electrode and a CR2032 coin cell as a simulated battery, the electrochemical performance of the negative electrode material prepared in this embodiment was evaluated. 1M NaClO4 (EC / DEC = 1:1 volume ratio) was used as the electrolyte, and glass fiber was used as the separator. The battery was assembled in an argon-filled glove box. Constant current charge-discharge tests were performed on a LAND CT2001 battery tester, with a charge-discharge range of 0.01V to 3.0V.

[0041] At 100mA·g -1 Its electrochemical performance was obtained by performing constant current charge-discharge tests, such as... Figure 4 The figure shows the battery's cycle performance and coulombic efficiency curves after 200 cycles. The prepared material can be clearly seen at 100 mA·g⁻¹. -1 The capacity remains at 1034 mAh·g after 200 cycles at the current density. -1 The material can also maintain excellent capacity retention during the cycling process.

[0042] Example 2

[0043] 10 kg of carbon nanotubes were added to 90 kg of 50% alcohol solution and ultrasonically treated. Then, 7 kg of 10% polyvinyl alcohol solution and 3 kg of 10% sodium carboxymethyl cellulose solution were added to the mixture. The mixture was stirred continuously at 200 rpm for 30 min to ensure thorough mixing and uniformity, thus obtaining the carbon nanotube slurry.

[0044] The carbon nanotube slurry was coated on the surface of an aluminum mesh and then fed into a liquid ammonia freezing dehydration tank via a transmission machine. It was then placed into a -10℃ low-temperature drying chamber to obtain an aerogel carbon nanotube coating / aluminum material.

[0045] The aerogel carbon nanotube coating / substrate continues to move forward and enters a 1 mol / L metallic potassium blue liquid ammonia solution, so that the aerogel is filled with this blue solution. Then it enters the evaporation chamber to evaporate the ammonia, thus obtaining a three-dimensional negative electrode material with pre-embedded potassium.

[0046] The battery anode material obtained in this embodiment has a thickness of 25 μm and an areal density of 16 g / m³. 2 The porosity is 66%. A CR2032 coin cell was assembled in an argon-filled glove box using a potassium metal sheet as the counter electrode, 1M KClO4 (EC / DEC = 1:1 volume ratio) as the electrolyte, and glass fiber as the separator. Constant current charge-discharge performance tests were conducted on a LAND battery testing system, with a charge-discharge range of 0.01V to 3.0V. The performance was tested at 20 mA·g. -1 After 200 cycles at the current density, the capacity still remains at 589.6 mAh·g. -1 The material can also maintain excellent capacity retention during the cycling process.

[0047] Example 3

[0048] 10 kg of carbon nanotubes were added to 90 kg of 40% alcohol solution and ultrasonically treated. Then, 7 kg of 10% polyvinyl alcohol solution and 3 kg of 10% sodium carboxymethyl cellulose solution were added to the mixture. The mixture was stirred continuously at 200 rpm for 30 min to ensure thorough mixing and uniformity, thus obtaining the carbon nanotube slurry.

[0049] The carbon nanotube slurry was coated onto the surface of copper foil, and then fed into a liquid ammonia freezing dehydration tank via a transmission machine. It was then placed into a -10℃ low-temperature drying chamber to obtain an aerogel carbon nanotube coating / copper material.

[0050] The aerogel carbon nanotube coating / substrate continues to move forward and enters a 1 mol / L metallic lithium blue liquid ammonia solution, so that the aerogel is filled with this blue solution. Then it enters the evaporation chamber to evaporate the ammonia, thus obtaining a three-dimensional negative electrode material with embedded lithium.

[0051] The battery anode material obtained in this embodiment has a thickness of 25 μm and an areal density of 20 g / m³. 2 The porosity is 60%. Using lithium metal as the counter electrode, Cellgard 2400 as the separator, and 1M LiPF6 (EC / DMC = 1:1 volume ratio) as the electrolyte, CR2032 coin cells were assembled in an argon-filled glove box. Constant current charge-discharge performance tests were conducted on a LAND battery testing system, with a charge-discharge range of 1.5V to 4.8V. The results were obtained at 20 mA·g. -1 The capacity remains at 1542 mAh·g after 500 cycles at the current density. -1 The material can also maintain excellent capacity retention during the cycling process.

[0052] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for producing a battery anode material, characterized by, It comprises the following steps: Step one, preparation of carbon nanotube slurry: carbon nanotubes are dispersed in a solvent, a certain amount of binder and stabilizer are added, and continuous stirring is carried out to make them fully mixed and uniform, thus obtaining the carbon nanotube slurry; wherein the concentration of the prepared carbon nanotube slurry is 10%-15%, and the mass ratio of carbon nanotubes, binder and stabilizer is 20-10:0.7:0.3; Step two, coating: the above-mentioned carbon nanotube slurry is coated on the surface of the substrate; Step three, freeze-drying: the coating / substrate is continuously forwarded into the liquid ammonia freeze-drying pool, and then into the low-temperature drying oven, to obtain the aerogel carbon tube coating / substrate; wherein the temperature range of the low-temperature drying oven is controlled at-33℃-0℃; Step four, pre-metallization: the aerogel carbon tube coating / substrate is continuously forwarded into the blue liquid ammonia solution of metal Li, Na or K, so that the aerogel is filled with the blue solution, and then into the evaporation chamber to evaporate ammonia, thus obtaining the three-dimensional negative electrode material with pre-embedded lithium, sodium or potassium element.

2. The method of claim 1, wherein the method further comprises the step of: In step one, the carbon nanotubes are at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes; ​ The purity of the carbon nanotubes is greater than 99%, the diameter is 10-200 nm, and the length is 5-20 μm.

3. The method of claim 1, wherein the method further comprises the step of: In step one, the solvent is at least one of deionized water, alcohol, ethylene glycol, propanol, isopropanol, acetone, N-methyl pyrrolidone; ​ The binder is at least one of polyvinylpyrrolidone, polyvinyl alcohol, polytetrafluoroethylene, lithium alginate, sodium alginate, potassium alginate, pectin acid lithium, pectin acid sodium, and pectin acid potassium; The stabilizer is sodium carboxymethyl cellulose.

4. The method of claim 1, wherein the method further comprises the step of adding a binder to the mixture of the carbon material and the lithium metal oxide. In step two, the substrate is a copper substrate, which is a copper foil or a copper mesh, and the corresponding blue solution in step four is a blue liquid ammonia solution of metal Li.

5. The method of claim 1, wherein the method further comprises the step of: In step two, the substrate is an aluminum substrate, which is an aluminum foil or an aluminum mesh, and the corresponding blue solution in step four is a blue liquid ammonia solution of metal Na or K. ​ 6. The method of claim 1, wherein the method further comprises: In step four, the concentration of the blue liquid ammonia solution is 0.5-1.5 mol / L.

7. A battery anode material, characterized by, The preparation method of any one of claims 1-6 is used.

8. Application of the battery negative electrode material of claim 7 in the production of lithium / sodium / potassium ion batteries.

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