Lithium-rich lithium ferrite as well as preparation method and application thereof
A lithium-rich lithium iron ferrite precursor was prepared by doping an organometallic source with a solvothermal method and then calcining it. Combined with carbon coating, the problem of high activation voltage in the synthesis of lithium-rich lithium iron ferrite was solved, and a lithium-ion battery supplement agent with low activation voltage and high performance was achieved.
Patent Information
- Application Number
- CN202511509212.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-01-13
AI Technical Summary
In the existing synthesis and modification processes of lithium iron ferrite, it is difficult to simultaneously achieve low activation voltage and high performance. Carbon-coated materials also have difficulty simultaneously improving conductivity, air stability, and reducing activation voltage.
A lithium-rich lithium ferrite precursor was synthesized by doping an organometallic source using a solvothermal method and then calcined to form a low-activation-voltage lithium ferrite. Its conductivity and air stability were improved by carbon coating.
The prepared low activation voltage lithium iron ferrite exhibits good lithium replenishment performance in lithium-ion batteries, improving battery life and long cycle performance.
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Figure CN121317889A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a lithium-rich lithium iron phosphate, its preparation method, and its applications. Background Technology
[0002] During the charge-discharge cycle of lithium-ion batteries, the formation of the solid electrolyte interphase (SEI) film plays a crucial role. It is a passivation layer formed by the reduction reaction of the electrolyte on the electrode surface, which can improve the performance and cycle life of lithium-ion batteries. However, the formation of the SEI film also consumes active lithium ions in the cathode material, reducing the number of lithium ions that can be inserted or removed, and lowering the capacity retention rate of lithium-ion batteries during cycles. As a result, lithium replenishment technology has emerged.
[0003] The cathode lithium replenishment technology is simple to operate, safe, and controllable. It requires no additions or alterations to the battery manufacturing process; simply adding a certain proportion of lithium replenishing agent during the cathode homogenization process can improve the performance of the prepared lithium-ion battery. In the field of cathode lithium replenishing agents, lithium-rich lithium iron phosphate (Li5FeO4) materials possess extremely high lithium replenishment capacity and exhibit good compatibility with existing lithium iron phosphate and ternary cathode materials, effectively enhancing their long-cycle performance. The charging platform of lithium-rich lithium iron phosphate is divided into two stages: the first stage is approximately 3.6V, and the second stage is approximately 3.9V. Before entering the first charging stage, a high potential energy barrier must be overcome to reach a high activation voltage before lithium-rich lithium iron phosphate can begin electrochemical decomposition. The activation voltage is related to both the synthesis and modification of lithium iron ferrite (LFP). The activation voltage of ordinary LFP is affected by the synthesis and modification processes, making it difficult to simultaneously achieve low activation voltage and high performance. The subsequent carbon coating material and method also influence the activation voltage, but the primary role of carbon coating is to increase the conductivity and air stability of LFP, allowing for the full release of lithium ions. Therefore, it is difficult to simultaneously increase conductivity, air stability, electrochemical performance, and reduce the activation voltage of LFP using only carbon coating. Summary of the Invention
[0004] The purpose of this invention is to provide a lithium-rich lithium iron ferrite, its preparation method and application, wherein the lithium-rich lithium iron ferrite has a low activation voltage, which can better improve the lithium replenishment performance.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing lithium iron ferrite rich in lithium, comprising the following steps: A precursor is obtained by mixing a lithium source, an iron source, an organometallic source, and an organic solvent and carrying out a solvothermal reaction. The precursor was calcined to obtain lithium iron ferrite rich in lithium; The organometallic source includes one or more of aluminum triethanolamine, manganese acetate, cobalt acetate, nickel acetate, and aluminum isopropoxide.
[0006] Preferably, the lithium source includes one or more of lithium peroxide, lithium oxide, and lithium hydroxide.
[0007] Preferably, the iron source includes one or more of ferric oxide, ferric oxide, and ferrous sulfate.
[0008] Preferably, the organic solvent includes n-heptane, ethanol, acetone, isopropanol, or acetonitrile.
[0009] Preferably, the molar ratio of lithium in the lithium source to iron in the iron source is 4.5~5.5:1.
[0010] Preferably, the mass of the organometallic source is 0-20% of the mass of the iron source and is not 0.
[0011] Preferably, the temperature of the solvothermal reaction is 80~200℃ and the time is 2~48h.
[0012] Preferably, the calcination is carried out under a protective atmosphere, and the calcination temperature is 400~900℃ for 1~20h.
[0013] This invention provides lithium ferrite rich in lithium prepared by the above preparation method.
[0014] This invention provides the application of the above-mentioned lithium-rich lithium iron phosphate in lithium-ion battery cathode materials as a lithium replenishing agent.
[0015] The beneficial effects of this invention are: This invention synthesizes a lithium-rich lithium iron ferrite precursor by doping with an organometallic source using a solvothermal method, followed by calcination to obtain lithium-rich lithium iron ferrite with a low activation voltage. During the solvothermal process, the lithium source, iron source, and organometallic source undergo an initial reaction, resulting in a deeper doping layer of the organometallic source in the precursor, which is incorporated into the crystal. During the high-temperature calcination, the organic components in the organometallic source decompose to form a local reducing atmosphere, reducing some of the ferric iron to ferrous iron and creating oxygen vacancies. This makes it easier for the metal components in the organometallic source to be incorporated into the crystal lattice, thereby reducing the electrochemical decomposition potential of lithium-rich lithium iron ferrite. Furthermore, its low activation voltage property is largely unaffected by subsequent carbon coating modification.
[0016] Carbon coating is applied directly to lithium-rich lithium iron ferrite with low activation voltage. After carbon coating, lithium-rich lithium iron ferrite with low activation voltage has better lithium replenishment performance, which is beneficial to improving the service life and long cycle performance of lithium-ion batteries. Attached Figure Description
[0017] Figure 1 Here is a scanning electron microscope image of lithium iron ferrite obtained in Example 1; Figure 2 The images show the XRD patterns of lithium-rich lithium ferrite obtained in Example 1 and lithium-rich lithium ferrite obtained in Comparative Example 1. Figure 3 The charging performance of lithium batteries prepared from lithium-rich lithium iron ferrite obtained in Example 1 and lithium-rich lithium iron ferrite obtained in Comparative Example 1 at a rate of 0.066C is shown in the graph. Figure 4 The graph shows the charging performance of the lithium battery prepared from lithium-rich lithium iron phosphate obtained in Example 2 at a rate of 0.066C. Detailed Implementation
[0018] This invention provides a method for preparing lithium iron ferrite rich in lithium, comprising the following steps: A precursor is obtained by mixing a lithium source, an iron source, an organometallic source, and an organic solvent and carrying out a solvothermal reaction. The precursor was calcined to obtain lithium iron ferrite rich in lithium; The organometallic source includes one or more of aluminum triethanolamine, manganese acetate, aluminum acetate, nickel acetate, and aluminum isopropoxide.
[0019] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.
[0020] In this invention, lithium source, iron source and organometallic source are uniformly dispersed in an organic solvent, and the resulting mixed dispersion is transferred to a hydrothermal reactor lined with polytetrafluoroethylene for solvothermal reaction. After cooling, the reaction liquid is taken out, and the precursor is obtained after solid-liquid separation.
[0021] In this invention, the lithium source preferably includes one or more of lithium peroxide, lithium oxide, and lithium hydroxide, and more preferably lithium peroxide. When there are multiple lithium sources, this invention does not have a special limitation on the mass ratio between the lithium sources. The iron source preferably includes one or more of ferric oxide, ferric oxide, and ferrous sulfate, and more preferably ferric oxide. When there are multiple iron sources, this invention does not have a special limitation on the mass ratio between the iron sources. The molar ratio of lithium in the lithium source to iron in the iron source is preferably 4.5~5.5:1, and more preferably 5.1~5.5:1.
[0022] In this invention, the organometallic source preferably includes one or more of aluminum triethanolamine, manganese acetate, cobalt acetate, nickel acetate, and aluminum isopropoxide, and more preferably aluminum isopropoxide. When there are multiple organometallic sources, this invention does not have a special limitation on the mass ratio between organometallic sources. The mass of the organometallic source is preferably 0 to 20% of the mass of the iron source and not 0, and more preferably 5 to 12% of the mass of the iron source.
[0023] In this invention, the organic solvent preferably includes n-heptane, ethanol, acetone, isopropanol or acetonitrile, and more preferably ethanol.
[0024] This invention does not specifically limit the solvothermal reaction method; heating and stirring or reacting in a homogeneous reactor are both acceptable. In the embodiments, it is preferred to carry out the reaction in a homogeneous reactor, and the preferred rotation speed is 30 r / min. In this invention, the temperature of the solvothermal reaction is preferably 80~200℃, more preferably 100~120℃, and the time is preferably 2~48h, more preferably 12~36h, and more preferably 24h.
[0025] The present invention does not have any particular limitation on the cooling method; natural cooling or accelerated cooling are both acceptable. In the embodiments, the preferred cooling method is natural cooling.
[0026] This invention does not have any particular limitation on the method of solid-liquid separation; vacuum drying or evaporation under a protective atmosphere are both acceptable. In the embodiments, the preferred method of solid-liquid separation is evaporation under an argon atmosphere.
[0027] In this invention, the precursor is preferably calcined under a protective atmosphere, cooled, and then removed to obtain lithium iron ferrite rich in lithium.
[0028] In this invention, the calcination is carried out under a protective atmosphere, preferably argon, the calcination temperature is preferably 400~900℃, more preferably 700~800℃, even more preferably 750℃, and the time is preferably 1~20h, more preferably 10~20h.
[0029] This invention provides lithium ferrite rich in lithium prepared by the above preparation method.
[0030] This invention provides the application of the above-mentioned lithium-rich lithium iron ferrite in lithium-ion battery cathode material lithium replenishment agent. The preferred method of application includes the following steps: mixing lithium-rich lithium iron ferrite with a carbon source, calcining, transferring the calcined material to a CVD furnace, introducing acetylene, and carbon coating to obtain carbon-coated lithium-rich lithium iron ferrite. The carbon-coated lithium iron ferrite was used as the positive electrode material, and was mixed with conductive carbon black and PVDF in N-methylpyrrolidone at a mass ratio of 80:10:10. The mixture was ground into a paste, coated onto aluminum foil, and vacuum dried at 120°C for 12 hours. The paste was then cut into electrode sheets with a diameter of 12 mm. The weighed electrode sheet was made into a positive electrode, lithium metal was used as a negative electrode, a polyethylene microporous membrane was used as a separator, and 1MLiClO4 (DME+PC) was used as an electrolyte. The lithium battery was assembled in a glove box filled with argon gas.
[0031] In this invention, the carbon source preferably includes glucose, sucrose or polyvinylpyrrolidone; the carbon coating temperature is preferably 400~700℃, more preferably 650℃, and the time is preferably 2~24h, more preferably 6h.
[0032] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0033] Example 1
[0034] 23.4 g of lithium peroxide, 16.1 g of ferric oxide and 1.8 g of aluminum isopropoxide were dispersed in n-heptane solvent and transferred to a polytetrafluoroethylene-lined hydrothermal reactor. The hydrothermal reactor was fixed in a homogeneous reactor and heated to 120 °C under a rotation speed of 30 r / min for 24 h for solvothermal reaction. After cooling to room temperature, the dispersion was taken out into a three-necked flask, argon gas was introduced into the three-necked flask, and the mixture was heated and stirred to evaporate, thus obtaining the precursor. The obtained precursor was transferred to a tube furnace and calcined at 750°C for 10 hours in an argon atmosphere. After naturally cooling to room temperature, it was taken out and pulverized to obtain lithium iron ferrite rich in lithium.
[0035] Example 2
[0036] 23.4 g of lithium peroxide, 16.1 g of ferric oxide and 1.5 g of aluminum triethanolamine were dispersed in ethanol solvent and transferred to a polytetrafluoroethylene-lined hydrothermal reactor. The hydrothermal reactor was fixed in a homogeneous reactor and heated to 100 °C under a rotation speed of 30 r / min for 12 h for solvothermal reaction. After cooling to room temperature, the dispersion was taken out into a three-necked flask, argon gas was introduced into the three-necked flask, and the mixture was heated and stirred to evaporate, thus obtaining the precursor. The obtained precursor was transferred to a tube furnace and calcined at 700°C for 10 hours in an argon atmosphere. After naturally cooling to room temperature, it was taken out and pulverized to obtain lithium iron ferrite rich in lithium.
[0037] Example 3
[0038] 23.4 g of lithium peroxide, 16.1 g of ferric oxide and 0.9 g of manganese acetate were dispersed in ethanol solvent and transferred to a polytetrafluoroethylene-lined hydrothermal reactor. The hydrothermal reactor was fixed in a homogeneous reactor and heated to 100 °C under a rotation speed of 30 r / min for 36 h of solvothermal reaction. After cooling to room temperature, the dispersion was taken out into a three-necked flask, argon gas was introduced into the three-necked flask, and the mixture was heated and stirred to evaporate, thus obtaining the precursor. The obtained precursor was transferred to a tube furnace and calcined at 800°C for 10 hours in an argon atmosphere. After naturally cooling to room temperature, it was taken out and crushed to obtain lithium iron ferrite rich in lithium.
[0039] Comparative Example 1
[0040] 23.4 g of lithium peroxide and 16.1 g of ferric oxide were ball-milled at 400 r / min for 2 h, calcined at 750 °C under argon atmosphere for 10 h, and then naturally cooled to room temperature before being crushed to obtain lithium-rich lithium iron oxide.
[0041] Characterization and performance testing
[0042] 1. Figure 1 The image shown is a scanning electron microscope image of the lithium-rich lithium iron phosphate obtained in Example 1. Figure 1 As shown, the particle size of lithium iron ferrite with low activation voltage is in the micrometer range.
[0043] 2. Figure 2 The XRD patterns of lithium-rich lithium ferrite obtained in Example 1 and Comparative Example 1 are shown below. Figure 2 As shown, the lithium-rich lithium iron ferrite phase with low activation voltage conforms to the standard card for lithium-rich lithium iron ferrite.
[0044] 3. ICP testing was performed on the lithium iron ferrite obtained in Example 1. The test results showed that the aluminum content was 0.82%, indicating that the lithium iron ferrite obtained in Example 1 was doped with aluminum.
[0045] 4. The lithium-rich lithium iron ferrite obtained in Examples 1 and 2 and the lithium-rich lithium iron ferrite obtained in Comparative Example 1 were assembled into lithium batteries according to the following methods. The electrochemical performance of the resulting lithium batteries was then tested, and the results are shown in the table below. Figures 3-4 ; Methods for assembling lithium batteries: Lithium-rich lithium iron ferrite was mixed with glucose at a mass ratio of 20:1 and calcined at 650°C. The calcined material was then transferred to a CVD furnace and carbon-coated with acetylene at 550°C. The carbon coating amount was 1%, resulting in carbon-coated lithium iron ferrite. Carbon-coated lithium iron ferrite was used as the positive electrode material. It was mixed with conductive carbon black and PVDF in N-methylpyrrolidone at a mass ratio of 80:10:10, ground into a paste, coated onto aluminum foil, vacuum dried at 120°C for 12 hours, and cut into electrode sheets with a diameter of 12 mm. The weighed electrode sheet was made into a positive electrode, lithium metal was used as a negative electrode, a polyethylene microporous membrane was used as a separator, and 1MLiClO4 (DME+PC) was used as an electrolyte. The lithium battery was assembled in a glove box filled with argon gas.
[0046] Figure 3 The graph shows the charging performance of lithium batteries prepared from lithium-rich lithium iron ferrite obtained in Example 1 and lithium-rich lithium iron ferrite obtained in Comparative Example 1 at a 0.066C rate. Figure 3As shown, the lithium battery prepared from lithium-rich lithium iron ferrite obtained in Example 1 achieves a specific charging capacity of 734 mAh / g at a rate of 0.066C and below 4.25V. The lithium battery prepared from lithium-rich lithium iron ferrite obtained in Comparative Example 1 achieves a specific charging capacity of 722 mAh / g at a rate of 0.066C and below 4.25V. From the specific capacity, it can be seen that the carbon-coated materials can effectively utilize the lithium replenishment performance of lithium-rich lithium iron ferrite. Regarding the activation voltage, the lithium battery prepared from lithium-rich lithium iron ferrite obtained in Example 1 has an activation voltage of 3.58V. After overcoming the potential energy barrier, the battery begins the first stage of plateau charging, with a plateau voltage of approximately 3.44V. In contrast, the battery prepared from the material obtained in Comparative Example 1 has an activation voltage of 4.11V. After overcoming the potential energy barrier, the battery begins the first stage of plateau charging, with a plateau voltage of approximately 3.51V. Both the activation voltage and the first stage charging plateau voltage of the battery prepared from the material obtained in Example 1 are higher than those of the battery prepared from the material obtained in Example 1. Figure 3 This invention demonstrates that the low activation voltage lithium iron ferrite prepared by the method of the present invention reduces the electrochemical decomposition potential barrier of lithium iron ferrite during charging, allowing lithium iron ferrite to decompose more gradually during lithium replenishment and better exert its lithium replenishment performance.
[0047] Figure 4 The graph shows the charging performance of the lithium battery prepared from lithium-rich lithium iron phosphate obtained in Example 2 at a rate of 0.066C. Figure 4 As shown, at a rate of 0.066C, the charging specific capacity below 4.25V reaches 781mAh / g, and the battery activation voltage is 3.68V. After overcoming the potential energy barrier, the battery begins the first stage of plateau charging, with a plateau voltage of approximately 3.45V.
[0048] As can be seen from the above embodiments, the present invention provides a method for preparing lithium iron phosphate rich lithium iron phosphate. The lithium iron phosphate rich lithium iron phosphate is prepared by solvothermal doping with organometallic salts. The activation voltage is low, which is 3.5~3.7V. This reduces the electrochemical decomposition potential energy barrier of lithium iron phosphate rich lithium iron phosphate, allowing lithium iron phosphate rich lithium iron phosphate to decompose more slowly during lithium replenishment. It is more in line with the charge and discharge range of lithium iron phosphate batteries and can better exert the lithium replenishment performance.
[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing lithium iron ferrite rich in lithium, characterized in that, Includes the following steps: A lithium source, an iron source, an organometallic source, and an organic solvent are mixed and subjected to a solvothermal reaction to obtain a precursor. The precursor was calcined to obtain lithium iron ferrite rich in lithium; The organometallic source includes one or more of aluminum triethanolamine, manganese acetate, cobalt acetate, nickel acetate, and aluminum isopropoxide.
2. The preparation method according to claim 1, characterized in that, The lithium source includes one or more of lithium peroxide, lithium oxide, and lithium hydroxide.
3. The preparation method according to claim 2, characterized in that, The iron source includes one or more of ferric oxide, ferric oxide, and ferrous sulfate.
4. The preparation method according to claim 1, characterized in that, The organic solvent includes n-heptane, ethanol, acetone, isopropanol, or acetonitrile.
5. The preparation method according to claim 1 or 3, characterized in that, The molar ratio of lithium in the lithium source to iron in the iron source is 4.5~5.5:
1.
6. The preparation method according to claim 1, characterized in that, The mass of the organometallic source is 0-20% of the mass of the iron source and is not zero.
7. The preparation method according to claim 1, characterized in that, The solvothermal reaction is carried out at a temperature of 80~200℃ for a time of 2~48h.
8. The preparation method according to claim 1, characterized in that, The calcination is carried out under a protective atmosphere at a temperature of 400-900°C for 1-20 hours.
9. Lithium-rich lithium iron ferrite prepared by the preparation method according to any one of claims 1 to 8.
10. The application of lithium iron ferrite as described in claim 9 in lithium-ion battery cathode materials as a lithium replenishing agent.