Preparation method and application of lithium iron phosphate composite material
By using one-dimensional structure carbon nanotubes and bacterial cellulose in electrode materials, the problem of limited conductivity of existing electrode materials is solved, and efficient electrochemical reactions and energy conversion are achieved, which is suitable for electrochemical systems that efficiently extract lithium.
Patent Information
- Application Number
- CN202411769873.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-04
- Publication Date
- 2025-03-18
AI Technical Summary
The conductivity of existing electrode materials is limited by two-dimensional structural conductive materials and poor dispersants, resulting in limited rate performance of electrochemical systems.
A one-dimensional structure carbon nanotube is used to mix with lithium iron phosphate, and a pore structure is constructed by combining bacterial cellulose to prepare a new lithium iron phosphate composite material, avoiding the interlayer stacking effect of two-dimensional conductive materials and the use of dispersants.
It improves the electrical conductivity and ion conductivity of the material, enhances the electrochemical reaction rate and energy conversion efficiency, and is suitable for electrochemical systems that efficiently improve lithium.
Smart Images
Figure CN119637835A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of lithium iron phosphate materials, and in particular to a preparation method and application of a lithium iron phosphate composite material. Background Art
[0002] With the rapid development of new energy vehicles and related industries, the global demand for lithium resources has risen sharply, prompting an urgent need for efficient and environmentally friendly lithium extraction technology from salt lake brine resources. Electrochemical deintercalation, as a new lithium extraction technology, has become a research focus due to its outstanding advantages in efficiency, selectivity and environmental friendliness. The construction of efficient electrode materials is crucial for the practical application of this technology.
[0003] The existing electrode manufacturing method adopts the method of coating a slurry containing active materials on aluminum foil or other current collectors. The obtained electrode performance is not only related to the active materials, but also to the dispersant used due to the adhesion effect between the coating and the current collector. Since the dispersant is a poor conductor of electrons, it will limit the electron movement ability of the conductive coating, thereby limiting the overall electrochemical system rate performance of the battery. At the same time, most of the conductive materials used in the existing electrodes are two-dimensional structures. Due to the influence of their layered structure, the mass transfer efficiency of the two-dimensional conductive materials is very low, which is not conducive to the working process of the electrode. Summary of the invention
[0004] The invention provides a method for preparing a lithium iron phosphate composite material with high transmission efficiency.
[0005] A method for preparing a lithium iron phosphate composite material comprises the following steps:
[0006] (1) mixing lithium iron phosphate, carbon nanotubes and bacterial cellulose in a mass ratio of 7-9:0.5-1.5:0.5-1.5, and then placing in a mold;
[0007] (2) Place the mold containing the sample horizontally in a freezer and freeze it at -60°C to -50°C for 12 to 24 hours to ensure that it is completely frozen and crystallized;
[0008] (3) The completely frozen crystallized sample is taken out and placed in a vacuum freeze dryer for drying at -60°C to -50°C for 24 to 48 hours to obtain a novel lithium iron phosphate composite material.
[0009] Further settings are:
[0010] In step (1):
[0011] The carbon nanotubes are added in the form of an aqueous solution with a mass concentration of 0.2%.
[0012] The bacterial cellulose is added in the form of an aqueous solution with a mass concentration of 1%.
[0013] The mass ratio of the lithium iron phosphate, carbon nanotubes and bacterial cellulose is 8:1:1 or 7:1.5:1.5 or 9:0.5:0.5.
[0014] The mixing can be carried out by stirring and / or ultrasonication.
[0015] In step (2):
[0016] The freezing treatment was performed at -50°C for 12 hours.
[0017] In step (3):
[0018] The drying process is carried out in a vacuum freeze dryer at -50°C for 24 hours.
[0019] The working principle of the present invention is as follows:
[0020] The inventor has found through research that the existing electrode manufacturing method uses a method of coating a slurry containing active materials on aluminum foil or other current collectors. The resulting electrode performance is not only related to the active materials, but also to the dispersant used due to the adhesion effect between the coating and the current collector. Since the dispersant is a poor conductor of electrons, it will limit the electron movement ability of the conductive coating, thereby limiting the overall electrochemical system rate performance of the battery. At the same time, most of the conductive materials used in the existing electrodes are two-dimensional structures. Due to the influence of their layered structure, the mass transfer efficiency of the two-dimensional conductive materials is very low, which is not conducive to the working process of the electrode.
[0021] The present invention uses carbon nanotubes, a one-dimensional structural material, and lithium iron phosphate to directly prepare a new lithium iron phosphate composite material, which avoids the interlayer stacking effect of two-dimensional conductive materials (such as graphene, transition metal sulfides, etc.) on the one hand, and avoids the use of dispersants on the other hand. The present invention uses carbon nanotubes as a conductive agent to enhance the conductivity of the material, introduces bacterial cellulose to construct a pore structure, and the prepared new lithium iron phosphate composite material has excellent ion conductivity.
[0022] Another object of the present invention is to provide an application of the lithium iron phosphate composite material prepared above in extracting lithium from salt lake brine. Since the lithium iron phosphate composite material of the present invention has excellent structural stability and ion conductivity, the extraction and embedding of lithium ions have no obvious effect on the crystal structure of the composite material, that is, Li + Ions can be smoothly embedded and extracted within the crystal lattice of the composite material without causing destructive effects on the main crystal framework, so it has excellent lithium extraction performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 The lithium iron phosphate composite materials with different mass ratios prepared in Examples 1-3 were in the voltage range of -0.8-1.2 V, 5 mV s -1 CV curves under scanning speed.
[0024] Figure 2 CV curves of the lithium iron phosphate composite material (mass ratio 7:1.5:1.5) prepared in Example 2 within the voltage range of -0.8-1.2V at different scan rates.
[0025] Figure 3 The lithium iron phosphate composite materials with different mass ratios prepared in Examples 1-3 were tested at 2.5 mV s -1 CV curves under sweep rate.
[0026] Figure 4 CV curves of the iron phosphate composite material (mass ratio 8:1:1) prepared in Comparative Example 1 within the voltage range of -0.8V-1.2V at different scan rates.
[0027] Figure 5 CV curves of the iron phosphate composite material (mass ratio 7:1.5:1.5) prepared in Comparative Example 2 within the voltage range of -0.8V-1.2V at different scan rates.
[0028] Figure 6 CV curves of the iron phosphate composite material (mass ratio 9:0.5:0.5) prepared in Comparative Example 3 within the voltage range of -0.8V-1.2V at different scan rates. DETAILED DESCRIPTION
[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described in combination with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0030] Example 1
[0031] A method for preparing a novel iron phosphate-based composite material comprises the following steps:
[0032] (1) The mass ratio of lithium iron phosphate, carbon nanotubes and bacterial cellulose is controlled to be 8:1:1, and the required materials are weighed respectively, wherein: carbon nanotubes and bacterial cellulose are made into aqueous solutions with mass concentrations of 0.2% and 1%, respectively, and then the three materials are mixed and stirred for 12 hours, and it is confirmed that there are no obvious particles or unevenness in the mixed solution, and then it is poured into a mold.
[0033] (2) Place the mold containing the sample horizontally in the freezer area of a refrigerator and freeze it at -50°C for 12 hours to ensure that it is completely frozen and crystallized.
[0034] (3) The completely frozen crystallized sample was taken out and placed in a vacuum freeze dryer for drying at -50°C for 24 hours to obtain a novel iron phosphate-based composite material labeled as LFP-8.
[0035] Example 2
[0036] The preparation method is the same as that in Example 1, except that the mass ratio of lithium iron phosphate, carbon nanotubes and bacterial cellulose is 7:1.5:1.5, and the obtained novel iron phosphate-based composite material is marked as LFP-7.
[0037] Example 3
[0038] The preparation method is the same as that of Example 1, except that the mass ratio of lithium iron phosphate, carbon nanotubes and bacterial cellulose is 9:0.5:0.5, and the obtained novel iron phosphate-based composite material is marked as LFP-9.
[0039] Comparative Example 1
[0040] The preparation method is the same as that of Example 1, except that the lithium iron phosphate is replaced by iron phosphate to prepare an iron phosphate composite material (mass ratio 8:1:1).
[0041] Comparative Example 2
[0042] The preparation method is the same as that of Example 2, except that the lithium iron phosphate is replaced by iron phosphate to prepare an iron phosphate composite material (mass ratio 7:1.5:1.5).
[0043] Comparative Example 3
[0044] The preparation method is the same as that of Example 3, except that the lithium iron phosphate is replaced by iron phosphate to prepare an iron phosphate composite material (mass ratio 9:0.5:0.5).
[0045] Performance Testing:
[0046] The electrochemical properties of the novel lithium iron phosphate composite materials prepared in Examples 1-3 and the iron phosphate composite materials prepared in Comparative Examples 1-3 were tested respectively.
[0047] Electrochemical performance test: Cut the material into 1cm*1cm square pieces, clamp them with platinum electrode clips as working electrodes, the counter electrode is a platinum electrode, the reference electrode is a saturated calomel electrode, and the electrolyte is 1M lithium chloride solution. Use Donghua DH7000C for electrochemical cyclic voltammetry test, the test conditions are as follows: voltage range is -0.8V-1.2V, scan rate is 5mVs -1 .
[0048] Test result analysis:
[0049] refer to Figure 1-3 Shown are the electrochemical test results of Examples 1 to 3, Figure 1-3 It is shown that the CV peak of the lithium iron phosphate composite material prepared in the embodiment of the present invention exhibits an obvious redox peak, and as the scan rate decreases, the redox peak becomes more obvious, indicating that the lithium iron phosphate composite material has good reversibility and ion kinematics performance.
[0050] contrast Figure 4-6 As shown, the redox peak of the comparative iron phosphate composite material is relatively gentle, and even if the scanning speed is reduced, the peak of the lithium iron phosphate composite material is not as significant, indicating that the reversibility and ion kinematics of the iron phosphate composite material are weaker than those of the lithium iron phosphate composite material.
[0051] analyze:
[0052] The present invention provides a new type of lithium iron phosphate composite material LiFePO4-CNTs-BC, which can be used in the electrochemical system of extracting lithium from salt lake brine. With the lithium insertion process as the core, the composite material integrates carbon nanotubes as a conductive agent to enhance the conductivity of the material, and introduces bacterial cellulose as a binder and constructs a pore structure, aiming to optimize the transmission path of lithium ions. Through experiments, we found that the prepared new type of lithium iron phosphate composite material LiFePO4-CNTs-BC has smaller ion and electron transmission barriers inside the composite material, and the charge transfer process is smoother, so it has a better electrochemical reaction rate and energy conversion efficiency, and can be used as an electrode material for efficiently and environmentally friendly extraction of brine resources in salt lakes.
[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a lithium iron phosphate composite material, characterized in that: The following steps are involved: (1) mixing lithium iron phosphate, carbon nanotubes and bacterial cellulose in a mass ratio of 7-9:0.5-1.5:0.5-1.5, and then placing in a mold; (2) Place the mold containing the sample horizontally in a freezer and freeze it at -60°C to -50°C for 12 to 24 hours to ensure that it is completely frozen and crystallized; (3) The completely frozen crystallized sample is taken out and placed in a vacuum freeze dryer for drying at -60°C to -50°C for 24 to 48 hours to obtain a novel lithium iron phosphate composite material.
2. The method for preparing a lithium iron phosphate composite material according to claim 1, characterized in that: In step (1): the carbon nanotubes are added in the form of an aqueous solution with a mass concentration of 0.2%.
3. The method for preparing a lithium iron phosphate composite material according to claim 1, characterized in that: In step (1): the bacterial cellulose is added in the form of an aqueous solution with a mass concentration of 1%.
4. The method for preparing a lithium iron phosphate composite material according to claim 1, characterized in that: In step (1): the mass ratio of lithium iron phosphate, carbon nanotubes and bacterial cellulose is 8:1:1 or 7:1.5:1.5 or 9:0.5:0.
5.
5. The method for preparing a lithium iron phosphate composite material according to claim 1, characterized in that: In step (1): the mixing is carried out by stirring and / or ultrasonication.
6. The method for preparing a lithium iron phosphate composite material according to claim 1, characterized in that: In step (2): the freezing treatment is carried out at -50°C for 12 hours.
7. The method for preparing a lithium iron phosphate composite material according to claim 1, characterized in that: In step (3): the drying process is carried out in a vacuum freeze dryer at -50°C for 24 hours.
8. Use of the lithium iron phosphate composite material prepared by the method of claim 1 in extracting lithium from salt lake brine.