Carbon-coated Li5AlO4 and preparation method, application thereof
By introducing carbon source confinement and precursor carbon coating process to hinder grain boundary migration during the Li5AlO4 synthesis stage, small-particle uniformly carbon-coated Li5AlO4 was prepared, solving the problem of particle morphology damage in the prior art and achieving simplified preparation process and performance improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HU NAN SHENG RONG KE JI YOU XIAN GONG SI
- Filing Date
- 2026-01-30
- Publication Date
- 2026-05-26
AI Technical Summary
In the preparation of Li5AlO4, existing technologies often use mechanical crushing methods such as high-energy ball milling or air jet milling, which can easily damage the integrity of the particle morphology, destroy its intrinsic structural characteristics, and affect the lithium replenishment effect.
Carbon source confinement is used to suppress particle coarsening during the crystal sintering process in the Li5AlO4 synthesis stage, and to hinder grain boundary migration and particle agglomeration during high-temperature treatment in the precursor carbon coating process. Carbon-coated Li5AlO4 is prepared by heat treatment and sintering.
Small-particle, uniformly carbon-coated Li5AlO4 products can be obtained without post-processing, simplifying the preparation process and improving material consistency and electrochemical performance.
Smart Images
Figure CN122079201A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium supplementation technology, specifically relating to a carbon-coated Li5AlO4, its preparation method, and its application. Background Technology
[0002] In recent years, Li5AlO4 has attracted attention as a novel lithium replenishing agent. Studies have shown that this material exhibits good performance during the initial charging to 4.3V (vs. Li + Irreversible decomposition can occur near the Li₂O₄ / Li₂O, with a typical reaction formula: Li₅AlO₄ → LiAlO₂ + 2Li₂O. Experimental data shows that this material molecule contains 5 lithium atoms, with a theoretical lithium content of 22.7%, higher than most existing lithium replenishing agents. It can achieve the same lithium replenishment effect with reduced addition amount, thereby reducing the impact on the positive electrode energy density. In addition, the decomposition product LiAlO₂ of Li₅AlO₄ has no lithium insertion / extraction activity within the 0~5V voltage window, exhibiting high stability. At the same time, LiAlO₂ is insoluble in conventional electrolytes and does not undergo continuous side reactions with the electrolyte; Li₂O is chemically inert and has good interfacial compatibility. This characteristic fundamentally avoids the consumption of active lithium by the decomposition products in subsequent cycles, realizing the irreversibility of the lithium replenishment process.
[0003] The lithium replenishment performance of Li5AlO4 is closely related to its particle size and specific surface area. Refining the particle size helps to improve the diffusion efficiency and reactivity of lithium ions. Existing technologies generally use post-processing techniques such as high-energy ball milling or air jet milling to achieve particle refinement. However, such mechanical crushing methods can easily damage the integrity of the particle morphology and destroy its intrinsic structural characteristics, which in turn has an adverse effect on the lithium replenishment effect. Summary of the Invention
[0004] Therefore, the purpose of this invention is to provide carbon-coated Li5AlO4, its preparation method, and its applications.
[0005] In a first aspect, the present invention provides a method for preparing carbon-coated Li5AlO4, comprising the following steps: S1: After mechanically mixing lithium source, aluminum source and carbon source evenly, a mixture is obtained; the mixture is heat-treated under an inert atmosphere to obtain a precursor; S2: After the precursor and carbon source are mechanically mixed evenly, they are sintered under an inert atmosphere to obtain carbon-coated Li5AlO4.
[0006] Preferably, in step S1, the lithium source is one or both of lithium hydroxide and lithium oxide; the aluminum source is aluminum oxide; and the carbon source is one or both of porous carbon and resin.
[0007] Preferably, in step S1, the molar ratio of Li in the lithium source to Al in the aluminum source is (5.01~5.15):1.
[0008] Preferably, in step S1, the mass of the carbon source is 1 to 10% of the total mass of the lithium source and the aluminum source.
[0009] Preferably, in step S1, the heat treatment temperature is 450~550℃ and the heat treatment time is 8~12h.
[0010] Preferably, in step S2, the carbon source is one or both of porous carbon and resin, and the mass of the carbon source is 3 to 7% of the precursor mass.
[0011] Preferably, in step S2, the sintering temperature is 600~750℃ and the sintering time is 8~12h.
[0012] Preferably, in steps S1 and S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.
[0013] Secondly, the present invention provides a carbon-coated Li5AlO4, which is prepared by the aforementioned preparation method.
[0014] Preferably, the carbon-coated Li5AlO4 has a D50 ≤ 3.6 μm.
[0015] Thirdly, the present invention provides a cathode material comprising the aforementioned carbon-coated Li5AlO4.
[0016] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: In the preparation method of this invention, the size control of Li5AlO4 particles is achieved through the confinement effect of the carbon source. Specifically, the carbon source introduced during the Li5AlO4 synthesis stage can effectively suppress particle coarsening during crystal sintering. Furthermore, in the precursor carbon coating process, the presence of the carbon source further hinders grain boundary migration and particle agglomeration during high-temperature treatment. The synergistic effect of the above-mentioned dual carbon regulation mechanism allows this invention to directly obtain small-particle, uniformly carbon-coated Li5AlO4 products without relying on post-processing techniques such as ball milling or air jet milling, significantly simplifying the preparation process and improving material consistency.
[0017] The preparation process of the uniformly carbon-coated Li5AlO4 product in this invention does not require a crushing step, thus avoiding damage to the particle morphology and the carbon coating layer, and can further improve the electrochemical performance of carbon-coated Li5AlO4. Attached Figure Description
[0018] Figure 1 The image shows a SEM image of carbon-coated Li5AlO4 prepared in Example 1.
[0019] Figure 2 The image shows a SEM image of carbon-coated Li5AlO4 prepared in Comparative Example 1.
[0020] Figure 3 SEM image of carbon-coated Li5AlO4 prepared for Comparative Example 2.
[0021] Figure 4 SEM image of carbon-coated Li5AlO4 prepared in Comparative Example 3.
[0022] Figure 5 The image shows a SEM image of the carbon-coated Li5AlO4 prepared in Example 2.
[0023] Figure 6 The image shows a SEM image of the carbon-coated Li5AlO4 prepared in Example 3. Detailed Implementation
[0024] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.
[0025] As mentioned above, in a first aspect, the present invention provides a method for preparing carbon-coated Li5AlO4, comprising the following steps: S1: After mechanically mixing lithium source, aluminum source and carbon source evenly, a mixture is obtained; the mixture is heat-treated under an inert atmosphere to obtain a precursor; S2: After the precursor and carbon source are mechanically mixed evenly, they are sintered under an inert atmosphere to obtain carbon-coated Li5AlO4.
[0026] In some embodiments, in step S1, the lithium source is one or both of lithium hydroxide and lithium oxide; the aluminum source is aluminum oxide; and the carbon source is one or both of porous carbon and resin.
[0027] In some embodiments, in step S1, the molar ratio of Li in the lithium source to Al in the aluminum source is (5.01~5.15):1.
[0028] In some embodiments, in step S1, the mass of the carbon source is 1 to 10% of the total mass of the lithium source and the aluminum source, including but not limited to: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.
[0029] In some embodiments, in step S1, the heat treatment temperature is 450~550℃, including but not limited to: 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, etc.; the heat treatment time is 8~12h, including but not limited to: 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, etc.
[0030] In some embodiments, in step S2, the carbon source is one or both of porous carbon and resin, and the mass of the carbon source is 3 to 7% of the precursor mass, including but not limited to: 3%, 4%, 5%, 6%, 7%, etc.
[0031] In some embodiments, in step S2, the sintering temperature is 600~750℃, including but not limited to: 600℃, 620℃, 650℃, 680℃, 700℃, 720℃, 750℃, etc.; the sintering time is 8~12h, including but not limited to: 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, etc.
[0032] In some embodiments, in steps S1 and S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.
[0033] Secondly, the present invention provides a carbon-coated Li5AlO4, which is prepared by the aforementioned preparation method.
[0034] In some embodiments, the carbon-coated Li5AlO4 has a D50 ≤ 3.6 μm.
[0035] Thirdly, the present invention provides a cathode material comprising the aforementioned carbon-coated Li5AlO4.
[0036] The porous carbon used in the examples has a particle size of less than 50 nm; the resin used is soft phenolic resin PF-81.
[0037] Example 1 S1: Lithium hydroxide, aluminum oxide and porous carbon (where the lithium-aluminum ratio of lithium hydroxide to aluminum oxide is 5.12:1, and the mass of porous carbon is 5% of the total mass of aluminum hydroxide and aluminum oxide) are stirred and mixed evenly to obtain a mixture; the mixture is placed in a reaction vessel and heat-treated to 500℃ for 10h under an inert atmosphere to obtain the precursor.
[0038] S2: The precursor and porous carbon are mixed evenly at a mass ratio of 10:0.5, and sintered at 700℃ for 10h under an inert atmosphere to obtain carbon-coated Li5AlO4.
[0039] The SEM image of the carbon-coated Li5AlO4 prepared in this embodiment is shown below. Figure 1 As shown, the carbon-coated Li5AlO4 has a smaller particle size.
[0040] Comparative Example 1 The process is basically the same as in Example 1, except that no carbon source is added in step S1, and the carbon source in step S1 is added to step S2 in order to maintain the same quality of the carbon source.
[0041] The specific preparation method is as follows: S1: After stirring and mixing lithium hydroxide and aluminum oxide (where the lithium-aluminum ratio of lithium hydroxide to aluminum oxide is 5.12:1) evenly, a mixture is obtained; the mixture is placed in a reaction vessel and heat-treated to 500℃ for 10 hours under an inert atmosphere to obtain the precursor.
[0042] S2: The precursor and porous carbon are mixed evenly at a mass ratio of 10:1, and sintered at 700℃ for 10h under an inert atmosphere to obtain carbon-coated Li5AlO4.
[0043] The SEM image of the carbon-coated Li5AlO4 prepared in this comparative example is shown below. Figure 2 As shown, the carbon-coated Li5AlO4 particles are significantly larger than those in Example 1.
[0044] Comparative Example 2 The carbon-coated Li5AlO4 prepared in Comparative Example 1 was subjected to air jet crushing.
[0045] In this comparative example, the carbon-coated Li5AlO4 particles prepared by airflow fragmentation in Comparative Example 1 are shown in the SEM image. Figure 3 As shown, the particles are significantly smaller compared to those in Comparative Example 1.
[0046] Comparative Example 3 It is basically the same as Example 1, except that no carbon source is added in step S2.
[0047] The specific steps are as follows: S1: Lithium hydroxide, aluminum oxide and porous carbon (where the lithium-aluminum ratio of lithium hydroxide to aluminum oxide is 5.12:1, and the mass of porous carbon is 10% of the total mass of aluminum hydroxide and aluminum oxide) are stirred and mixed evenly to obtain a mixture; the mixture is placed in a reaction vessel and heat-treated to 500℃ for 10h under an inert atmosphere to obtain the precursor.
[0048] S2: The precursor is stirred and mixed evenly, and sintered at 700℃ for 10h under an inert atmosphere to obtain carbon-coated Li5AlO4.
[0049] The SEM image of the carbon-coated Li5AlO4 prepared in this comparative example is shown below. Figure 4 As shown, the carbon-coated Li5AlO4 particles are significantly larger than those in Example 1.
[0050] Example 2 Compared with Example 1, the difference is that the amount of porous carbon added in step S1 is 1% of the total mass of aluminum hydroxide and aluminum oxide.
[0051] The SEM image of the carbon-coated Li5AlO4 prepared in this embodiment is shown below. Figure 5 As shown, the particle size of the particles is increased compared to that of Example 1. This may be because the amount of porous carbon added is too small, which is not enough to suppress the grain size.
[0052] Example 3 Compared with Example 1, the difference is that the amount of porous carbon added in step S1 is 10% of the total mass of aluminum hydroxide and aluminum oxide.
[0053] The SEM image of the carbon-coated Li5AlO4 prepared in this embodiment is shown below. Figure 6 As shown, the particle size change is not significant compared to that of Example 1, indicating that adding too much porous carbon does not further reduce the particle size.
[0054] Example 4 It is basically the same as Example 1, except that the porous carbon is replaced with resin.
[0055] Example 5 S1: Lithium oxide, aluminum oxide and resin (where the lithium oxide to aluminum oxide ratio is 5.15:1, and the mass of the resin is 7% of the total mass of aluminum hydroxide and aluminum oxide) are stirred and mixed evenly to obtain a mixture; the mixture is placed in a reaction vessel and heated to 450℃ for 12 hours under an inert atmosphere to obtain the precursor.
[0056] S2: The precursor and resin are mixed evenly at a mass ratio of 10:0.3, and sintered at 600℃ for 12 hours under an inert atmosphere to obtain carbon-coated Li5AlO4.
[0057] Example 6 S1: Lithium oxide, aluminum oxide and resin (where the lithium oxide to aluminum oxide ratio is 5.02:1, and the mass of the resin is 3% of the total mass of aluminum hydroxide and aluminum oxide) are stirred and mixed evenly to obtain a mixture; the mixture is placed in a reaction vessel and heat-treated at 550℃ for 8 hours under an inert atmosphere to obtain the precursor.
[0058] S2: The precursor and porous carbon are mixed evenly at a mass ratio of 10:0.7, and sintered at 750℃ for 8 hours under an inert atmosphere to obtain carbon-coated Li5AlO4.
[0059] The D50, powder resistance (the powder resistance of the material was tested using a four-probe sheet resistance tester), and specific surface area of the carbon-coated Li5AlO4 prepared in Examples 1-5 and Comparative Examples 1-2 were tested. The test results are shown in Table 1.
[0060] Table 1 As can be seen from the data in Table 1, the carbon-coated Li5AlO4 prepared in Example 1 has a smaller D50, lower powder resistance, and higher specific surface area. The carbon-coated Li5AlO4 prepared in Comparative Example 1 shows a significant increase in D50 and powder resistance compared to Example 1, while its specific surface area decreases. In Comparative Example 2, the carbon-coated Li5AlO4 prepared using airflow crushing showed a significant decrease in particle size compared to Comparative Example 1, but a significant increase in powder resistance. In Comparative Example 3, no carbon source was added in step S2, resulting in a significant increase in D50 and powder resistance of the prepared carbon-coated Li5AlO4 compared to Example 1, while its specific surface area decreased. In Example 2, the amount of porous carbon added in step S1 was reduced, resulting in a significant increase in D50 and powder resistance, and a significant decrease in specific surface area, in the prepared carbon-coated Li5AlO4. In Example 3, the amount of porous carbon added in step S1 was further increased. The D50 of the carbon-coated Li5AlO4 did not decrease further, but the powder resistance decreased further, and the specific surface area decreased significantly. In Example 4, the D50 of the carbon-coated Li5AlO4 prepared by replacing porous carbon with resin changed little compared to Example 1, but the powder resistance increased, and the specific surface area decreased. In Examples 5 and 6, the corresponding preparation process parameters were adjusted, and the D50, powder resistance, and specific surface area of the carbon-coated Li5AlO4 prepared showed some fluctuation, but overall, the results were good.
[0061] The carbon-coated Li5AlO4 prepared in Examples 1-5 and Comparative Examples 1-2 were respectively mixed with conductive agent Super-P and binder PVDF in a ratio of 8:1:1 to prepare slurries. The slurries were coated on aluminum foil to form positive electrode sheets, and lithium metal sheets were used as negative electrode sheets. The slurries were assembled into simulated batteries and charged at 0.066C with a voltage range of 2.0 to 4.3V. The test results are shown in Table 2.
[0062] Table 2 As can be seen from the data in Table 2, the carbon-coated Li5AlO4 prepared in Example 1 has a higher specific charge capacity. The specific charge capacity of the carbon-coated Li5AlO4 prepared in Comparative Example 1 is significantly lower than that of Example 1, possibly because its particle size is too large, hindering lithium-ion migration and leading to a decrease in specific charge capacity. In Comparative Example 2, airflow fragmentation was performed on the basis of Comparative Example 1, resulting in a certain increase in specific charge capacity compared to Comparative Example 1, but the improvement is not significant. This may be because airflow fragmentation disrupts the grain structure of Li5AlO4, and when the particles are fragmented, more uncoated contact surfaces are exposed, increasing powder resistance. Ultimately, although the particle size decreases, the performance improvement is not significant. The specific charge capacity of the carbon-coated Li5AlO4 prepared in Comparative Example 3 was significantly lower than that in Example 1, possibly because its particle size was too large, hindering lithium-ion migration and thus reducing the specific charge capacity. The specific charge capacity of the carbon-coated Li5AlO4 prepared in Example 2 also showed a significant decrease compared to Example 1, possibly because the amount of porous carbon added was too small, limiting its effect on inhibiting grain growth. The specific charge capacity of the carbon-coated Li5AlO4 prepared in Example 3 was slightly lower than that in Example 1, possibly because the amount of carbon added was too large, affecting the performance of Li5AlO4. The specific charge capacity of the carbon-coated Li5AlO4 prepared in Example 4 using resin instead of porous carbon was somewhat lower than that in Example 1. In Examples 5 and 6, the preparation process parameters were adjusted, resulting in some fluctuation in the specific charge capacity of the prepared carbon-coated Li5AlO4, but all exhibited relatively high specific charge capacities.
[0063] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing carbon-coated Li5AlO4, characterized in that, Includes the following steps: S1: After mechanically mixing lithium source, aluminum source and carbon source evenly, a mixture is obtained; the mixture is heat-treated under an inert atmosphere to obtain a precursor; S2: After the precursor and carbon source are mechanically mixed evenly, they are sintered under an inert atmosphere to obtain carbon-coated Li5AlO4.
2. The method for preparing carbon-coated Li5AlO4 according to claim 1, characterized in that, In step S1, the lithium source is one or both of lithium hydroxide and lithium oxide; the aluminum source is aluminum oxide; and the carbon source is one or both of porous carbon and resin.
3. The method for preparing carbon-coated Li5AlO4 according to claim 1, characterized in that, In step S1, the molar ratio of Li in the lithium source to Al in the aluminum source is (5.01~5.15):1; And / or: the mass of the carbon source is 1 to 10% of the total mass of the lithium source and the aluminum source.
4. The method for preparing carbon-coated Li5AlO4 according to claim 1, characterized in that, In step S1, the heat treatment temperature is 450~550℃ and the heat treatment time is 8~12h.
5. The method for preparing carbon-coated Li5AlO4 according to claim 1, characterized in that, In step S2, the carbon source is one or both of porous carbon and resin, and the mass of the carbon source is 3 to 7% of the precursor mass.
6. The method for preparing carbon-coated Li5AlO4 according to claim 1, characterized in that, In step S2, the sintering temperature is 600~750℃ and the sintering time is 8~12h.
7. The method for preparing carbon-coated Li5AlO4 according to claim 1, characterized in that, In steps S1 and S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.
8. A carbon-coated Li5AlO4, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 7.
9. The carbon-coated Li5AlO4 according to claim 8, characterized in that, The particle size D50 of the carbon-coated Li5AlO4 is ≤3.6μm.
10. A positive electrode material, characterized in that, This includes carbon-coated Li5AlO4 prepared by any of the preparation methods of claims 1 to 7, or carbon-coated Li5AlO4 as described in any of claims 8 to 9.