CN109167028B - Regeneration preparation method of lithium iron phosphate/carbon composite material - Google Patents
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Abstract
The invention relates to a regeneration preparation method of a lithium iron phosphate/carbon composite material, which comprises the following steps: performing airflow collision crushing on powder which is subjected to abnormal oxidation in the oxygen-free sintering process of the lithium iron phosphate, fully crushing and sintering aggregates and stripping amorphous carbon on the surface layer of the material; crushing and dispersing the crushed oxidized and sintered powder through ultrasonic vibration, and separating amorphous carbon by using induced air cyclone to obtain an abnormally oxidized lithium iron phosphate material; weighing and mixing the crushed and stripped amorphous carbon lithium iron phosphate with a carbon source and a lithium salt, grinding at a high speed, pre-pressing by a pair of rollers, and sintering in an oxygen-free atmosphere to realize the regeneration of the lithium iron phosphate/carbon composite material. The method has simple process, low energy consumption and excellent performance of the regenerated product, and is favorable for reducing the rejection rate of abnormal oxidation in the production process of the lithium iron phosphate material.
Description
Technical Field
The invention relates to the technical field of battery material preparation, in particular to a regeneration preparation method of a lithium iron phosphate/carbon composite material.
Background
The olivine-structured lithium iron phosphate is a novel lithium ion battery anode material, the theoretical capacity of the lithium iron phosphate is 170mAh/g, and the voltage of the lithium iron phosphate on a lithium platform is about 3.5V. The strong covalent bond in the lithium iron phosphate can keep the high stability of the crystal structure in the charging and discharging process, so that the lithium iron phosphate has higher safety performance and longer cycle service life than other anode materials. In addition, the space valence bond structure of the lithium iron phosphate material ensures that the lithium iron phosphate material has strong thermodynamic and kinetic stability, and is still stable when heated to 200 ℃ in the air atmosphere under normal pressure. Compared with other anode materials, the lithium iron phosphate has excellent safety performance and excellent cycle stability, so that the material has wider application field and rapidly shows the outstanding competitive advantage.
At present, the industrialized production process of lithium iron phosphate mostly adopts the mixing of iron phosphate and lithium salt and the addition of a carbon source to carry out anaerobic calcination to synthesize the lithium iron phosphate/carbon composite material. The equipment used in the production process mostly adopts a roller kiln filled with nitrogen gas to carry out anaerobic sintering. With the pursuit of productivity and efficiency, production equipment is continuously increased and lengthened, a certain amount of air enters a hearth due to abnormal leakage points caused by equipment failure and the like in the actual use process, the loss of amorphous carbon is accelerated due to the increase of oxygen content of materials in a high-temperature calcination stage, even the iron lithium phosphate material is oxidized, and the valence state of iron ions is changed to generate red ferric iron. The production equipment fails due to the follow-up yield of the production equipment and cannot be stopped in time, so that the large-batch lithium iron phosphate material is unqualified in oxidation.
In the prior art, the material is mainly oxidized at high temperature and then reduced. For example, CN 102208706 a (a method for recycling and regenerating a positive electrode material of a waste lithium iron phosphate battery) considers that the internal components of the waste lithium iron phosphate battery are complex, the method includes first stripping and collecting the positive electrode material in the waste battery, performing high-temperature aerobic calcination to remove positive electrode additives, carbon and other substances, then adding lithium salt, a carbon source and the like to perform mixed grinding, and finally placing the mixed powder in a non-oxidizing atmosphere to perform high-temperature calcination.
In the method for regenerating abnormal materials, CN 102064366 a provides a similar treatment method, in which waste lithium iron phosphate is heated and fully oxidized in air, then a carbon source is added and mixed, and the mixture is subjected to high-temperature calcination and cooling in a protective atmosphere, and then the mixture is taken out to obtain a target product.
According to the existing method, a high-temperature oxidation, calcination, impurity removal and screening method is adopted for the positive pole piece and the abnormal lithium iron phosphate material, and then the overoxidized powder is added with lithium salt and a carbon source to perform anaerobic sintering reduction to obtain a target product, so that more uncontrollable risks are increased in the material manufacturing process and the material regeneration difficulty is improved.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a regeneration preparation method of a lithium iron phosphate/carbon composite material, so that the regeneration of an abnormally oxidized lithium iron phosphate/carbon composite material in the industrial production process is realized, the rejection rate of the lithium iron phosphate material is reduced, and the risks of overburning, over reduction or incomplete reduction and the like in the material regeneration process are reduced.
In order to achieve the purpose, the invention adopts the following technical scheme:
a regeneration preparation method of a lithium iron phosphate/carbon composite material comprises the following steps:
s1, collecting sintering powder of the lithium iron phosphate/carbon composite material which is abnormally oxidized in the sintering process, crushing the sintering powder by using an airflow crushing device, and then screening fine powder in a grading manner;
s2, carrying out ultrasonic vibration crushing on the fine powder obtained in the step S1, and meanwhile conveying the powder into a cyclone separator through backfilling induced air flow to realize the separation of the abnormally sintered lithium iron phosphate fine powder from surface coated carbon;
s3, detecting the content of lithium and iron elements in the abnormally sintered lithium iron phosphate fine powder separated by the S2 by an element analysis method, adding lithium salt to enable the molar ratio of the lithium to the iron elements in the mixture to be 1.1-1.2:1, then adding a carbon source, and stirring and mixing uniformly by a dry method;
and S4, fully grinding the powder after stirring and mixing, pre-pressing, compacting, and sintering in an oxygen-free atmosphere to obtain the regenerated lithium iron phosphate/carbon composite material.
Further, the jet milling device can be one of a flat jet mill, a fluidized bed opposite-jet mill, a circulating pipe jet mill, an opposite-jet mill and a target jet mill.
Furthermore, the granularity of the fine powder in the S1 is required to be D50 not more than 300nm and D100 not more than 900 nm.
Further, the cyclone separator is a spiral cyclone separator; and collecting the lithium iron phosphate fine powder with higher specific gravity by a centrifugal sedimentation principle to realize the separation of the abnormal sintering lithium iron phosphate and the amorphous carbon.
Further, the elemental analysis method may be ICP atomic emission spectrometry or atomic absorption spectrometry.
Further, the lithium salt is eutectic point mixed lithium salt added with lithium fluoride, and the molar ratio of the lithium fluoride is 1-2%; the eutectic point mixed lithium salt may be lithium hydroxide-lithium carbonate, lithium hydroxide-lithium chloride, lithium hydroxide-lithium nitrate, lithium nitrate-lithium chloride, or the like.
Further, the carbon source is 80% by weight of glucose and 20% by weight of one or more of food-grade sucrose, maltose and fructose.
Further, the powder stirred and mixed in the step S4 is ground for 3-5 hours by a high-speed ball mill, and then is pre-pressed by a pair of rollers, wherein the gap between the pair of rollers is 2 mm; the crucible filling and calcining are carried out after the material is compacted, so that the method is favorable for increasing the contact tightness in the sintering process of the material and improving the compaction density of the material at the coating end of the battery core.
Further, the oxygen-free sintering atmosphere is one or more of nitrogen, argon and helium; the temperature of the anaerobic sintering constant-temperature area is 300-450 ℃, and the heat preservation time is 4-7 hours.
The invention has the following beneficial effects: the invention provides a regeneration preparation method of a lithium iron phosphate/carbon composite material, which is characterized in that airflow collision crushing is carried out on sintered powder which is oxidized abnormally in the production process, sintered agglomerate particles are all opened, original sintered particles are crushed, lithium iron phosphate sintered fine powder is obtained, and coated amorphous carbon is stripped from the surface layer of the powder material. The lithium iron phosphate powder with extremely low carbon content and abnormal sintering is obtained by ultrasonic vibration and induced air cyclone screening, and a foundation is laid for subsequent carbon recoating.
The disclosed technology generally adopts aerobic high-temperature calcination to remove carbon, so that not only is the energy consumption high, the material is over-sintered and the lithium iron phosphate is over-oxidized, more reducing agents are needed for reducing ferric iron, but also the possibility of over-reduction or incomplete reduction of iron elements exists, the performance of the material is greatly reduced, and the quality risk of the material is increased.
The collected abnormal lithium iron phosphate powder with extremely low carbon content and sintering is mixed with lithium salt and a carbon source, and the used lithium salt is eutectic salt with low melting point, so that the used calcining temperature is relatively low, the calcining time is short, and the performance inactivation caused by overburning of the material is avoided. In addition, the reasonable preparation of the eutectic lithium salt component and the dry-method stirring and uniform grinding of the powder are beneficial to more regular granulation of the material in the sintering process through the double-roller prepressing. The regenerated material has electrical property which is higher than that of a normal material, and the positive pole piece has higher material compaction density when the battery cell is manufactured, so that the monomer energy density of the battery cell is further improved.
The regenerated lithium iron phosphate/carbon composite material is prepared into a CR2016 type button battery with a lithium sheet as a cathode for charge-discharge test, the initial discharge specific capacity of 0.2C is 158-162mAh/g, the coulombic efficiency is 96-99%, the average discharge specific capacity of 1C is 148-154mAh/g, the average discharge specific capacity of 2C is 137-143mAh/g, and the electrical property is excellent.
Drawings
Fig. 1 is an SEM photograph of a lithium iron phosphate/carbon composite material regenerated in example 1; as can be seen from figure 1, the material is solid spherical particles, the appearance is relatively regular, the gaps of fine powder are small, and the agglomeration molding is better.
FIG. 2 is an XRD pattern of a lithium iron phosphate/carbon composite material regenerated in example 1; it can be seen from fig. 2 that the composite material of the present invention has a higher purity and a better crystallinity.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the embodiments. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The following examples were used to make CR2016 button cells and to test the electrochemical performance of the materials as follows:
(1) and (3) preparing a battery positive plate, namely weighing a sample from the regenerated lithium iron phosphate/carbon composite material and a binder polyvinylidene fluoride (PVDF) according to the mass ratio of 8: 2. Mixing and dissolving a binder and an organic solvent N-methyl pyrrolidone (NMP), adding a fully ground lithium iron phosphate/carbon composite material, stirring into slurry, coating the slurry on the surface of a carbon-coated aluminum foil, drying and rolling to obtain the battery positive plate.
(2) Assembling the battery: and stamping the rolled positive plate into a positive plate with the diameter of 12mm, accurately weighing, and converting the effective mass of the lithium iron phosphate/carbon composite material according to the composition of the positive plate. The prepared positive plate, electrolyte, a PE diaphragm with the diameter of 16mm and a lithium sheet with the diameter of 15mm are used for assembling the button cell in a glove box.
(3) And (3) performance testing: the specific capacity test of the battery uses a Shenzhen Xinwei battery test system, the test temperature is 25 ℃, and the charge and discharge multiplying power of 0.2C, 1C and 2C is respectively subjected to 10 times of cycle test.
The raw material collection steps of each example are as follows:
collecting reddish abnormal sintering powder which is excessively oxidized due to serious standard exceeding of oxygen content in a hearth caused by faults of a sintering kiln in the production process of a production line, and testing the carbon content by a carbon-sulfur analyzer to be only 0.95 percent. The 0.2C specific discharge capacity of the material is only 125mAh/g according to the CR2016 electricity-deducting test method, and the charge-discharge curve is accompanied by serious polarization phenomenon.
And (2) crushing the abnormal lithium iron phosphate sintering material by using compressed air by adopting an air flow crushing device (such as a flat air flow mill, a fluidized bed opposite-jet air flow mill, a circulating pipe air flow mill, an opposite-jet air flow mill and a target air flow mill), wherein the pressure of the used compressed air is more than or equal to 0.5MPa, and the crushed powder is screened and collected by a grading motor, wherein D50 is less than or equal to 300nm, and D100 is less than or equal to 900 nm. And carrying out ultrasonic vibration crushing on the collected fine powder, conveying the powder to a cyclone separator by using induced air backfill airflow, and separating and screening the lithium iron phosphate powder and the stripped amorphous carbon to obtain the abnormal oxidized lithium iron phosphate fine powder with extremely low carbon content.
The cyclone separator is a spiral cyclone separator; and collecting the lithium iron phosphate fine powder with higher specific gravity by a centrifugal sedimentation principle to realize the separation of the abnormal sintering lithium iron phosphate and the amorphous carbon.
Collecting abnormal oxidized lithium iron phosphate fine powder with extremely low carbon content, and detecting the abnormal oxidized lithium iron phosphate fine powder by an element analysis method (ICP atomic emission spectrometry or atomic absorption spectrometry can be adopted) to obtain the powder with the molar ratio of lithium to iron of 0.97:1, which indicates that slight lithium loss occurs in the over-oxidation process and corresponding lithium source compounds need to be supplemented in the subsequent regeneration process.
Example 1
Accurately weighing 100g of an abnormal oxidized lithium iron phosphate fine powder raw material sample with extremely low carbon content obtained by crushing, separating and screening, adding lithium hydroxide-lithium carbonate eutectic point mixed lithium salt and lithium fluoride, wherein the molar ratio of the lithium fluoride is 1%, adjusting the molar ratio of lithium to iron in the sample to be 1.1:1, adding 8g of glucose and 2g of food-grade sucrose, stirring and mixing uniformly by a dry method, grinding the mixed powder in a high-speed ball mill for 5h, collecting the ball-milled sample, heating to 300 ℃ at a heating rate of 5 ℃/min in a nitrogen protective atmosphere after pre-pressing by a pair roller (the gap between the pair roller is 2 mm), preserving heat for 7h, and cooling the material to room temperature to obtain the regenerated lithium iron phosphate/carbon composite material. The carbon content is 1.35 percent and the tap density of the material is 1.0g/cm detected by a carbon-sulfur analyzer3The compaction density of the positive pole piece of the battery core can reach 2.4g/cm3And the capacity of the single battery cell is greatly improved.
The lithium iron phosphate/carbon composite material regenerated in the example 1 is charged and discharged at 0.2C, 1C and 2C multiplying powers by assembling a button type half cell, and the test result is as follows: the discharge specific capacities corresponding to the multiplying powers of 0.2C, 1C and 2C are 161mAh/g, 150mAh/g and 141mAh/g in sequence, which shows that the regenerated composite material has higher specific capacity and multiplying power performance.
Example 2
Accurately weighing 100g of an abnormal oxidized lithium iron phosphate fine powder raw material sample with extremely low carbon content obtained by crushing, separating and screening, adding lithium hydroxide-lithium nitrate eutectic point mixed lithium salt and lithium fluoride, wherein the molar ratio of the lithium fluoride is 1.5%, adjusting the molar ratio of lithium to iron in the sample to be 1.15:1, adding 8g of glucose and 2g of maltose, stirring and mixing uniformly by a dry method, grinding the mixed powder in a high-speed ball mill for 3h, collecting the ball-milled sample, heating to 450 ℃ at the heating rate of 5 ℃/min in a helium protective atmosphere after pre-pressing (the clearance between double rollers is 2 mm), preserving heat for 4h, and cooling the material to room temperature to obtain the regenerated lithium iron phosphate/carbon composite material. The carbon content is 1.5 percent and the tap density of the material is 0.9g/cm detected by a carbon-sulfur analyzer3Positive pole piece pressure of battery cellThe solid density can reach 2.35g/cm3And the capacity of the single battery cell is greatly improved.
The electrical property analysis of the lithium iron phosphate/carbon composite material obtained in this example was performed in the same test manner as in example 1, and the electrical property test result was: the discharge specific capacities corresponding to the multiplying powers of 0.2C, 1C and 2C are 158mAh/g, 148mAh/g and 138mAh/g in sequence, which shows that the regenerated composite material has higher specific capacity and multiplying power performance.
Example 3
Accurately weighing 100g of an abnormal oxidized lithium iron phosphate fine powder raw material sample with extremely low carbon content obtained by crushing, separating and screening, adding lithium hydroxide-lithium chloride eutectic point mixed lithium salt and lithium fluoride, wherein the molar ratio of the lithium fluoride is 2%, adjusting the molar ratio of lithium to iron in the sample to be 1.2:1, adding 8g of glucose and 2g of fructose, stirring and mixing uniformly by a dry method, grinding the mixed powder in a high-speed ball mill for 3h, collecting the ball-milled sample, heating to 450 ℃ at a heating rate of 5 ℃/min in an argon protective atmosphere after pre-pressing by a pair roller (the gap between the pair roller is 2 mm), preserving heat for 7h, and cooling the material to room temperature to obtain the regenerated lithium iron phosphate/carbon composite material. The carbon content is 1.38 percent and the tap density of the material is 1.03g/cm detected by a carbon-sulfur analyzer3The compaction density of the positive pole piece of the battery core can reach 2.38g/cm3And the capacity of the single battery cell is greatly improved.
The electrical property analysis of the lithium iron phosphate/carbon composite material obtained in this example was performed in the same test manner as in example 1, and the electrical property test result was: the discharge specific capacities corresponding to the multiplying powers of 0.2C, 1C and 2C are 160mAh/g, 149mAh/g and 140mAh/g in sequence, which shows that the regenerated composite material has higher specific capacity and multiplying power performance.
Example 4
Accurately weighing 100g of an abnormal oxidized lithium iron phosphate fine powder raw material sample with extremely low carbon content obtained by crushing, separating and screening, adding lithium nitrate-lithium chloride eutectic point mixed lithium salt and lithium fluoride, wherein the molar ratio of the lithium fluoride is 1%, adjusting the molar ratio of lithium to iron in the sample to be 1.15:1, adding 8g of glucose and 2g of maltose, stirring and mixing uniformly by a dry method, grinding the mixed powder in a high-speed ball mill for 4 hours, and grinding the mixed powderCollecting ball-milled samples, pre-pressing the ball-milled samples by a pair of rollers (the gap between the pair of rollers is 2 mm), heating the ball-milled samples to 450 ℃ at a heating rate of 5 ℃/min in a nitrogen protective atmosphere, then preserving the heat for 6 hours, and cooling the material to room temperature to obtain the regenerated lithium iron phosphate/carbon composite material. The carbon content is 1.45 percent and the tap density of the material is 1.0g/cm detected by a carbon-sulfur analyzer3The compaction density of the positive pole piece of the battery core can reach 2.39g/cm3And the capacity of the single battery cell is greatly improved.
The electrical property analysis of the lithium iron phosphate/carbon composite material obtained in this example was performed in the same test manner as in example 1, and the electrical property test result was: the discharge specific capacities corresponding to the multiplying powers of 0.2C, 1C and 2C are 160mAh/g, 152mAh/g and 142mAh/g in sequence, which shows that the regenerated composite material has higher specific capacity and multiplying power performance.
Comparative example 1
The lithium iron phosphate/carbon composite material prepared in normal production is subjected to performance analysis according to the same test mode of the example 1, the carbon content is 1.45 percent, and the tap density of the material is 0.91g/cm3The cell compaction density is 2.23g/cm3The electrical property test results are as follows: the specific capacities corresponding to the multiplying powers of 0.2C, 1C and 2C are 160mAh/g, 148mAh/g and 137mAh/g in sequence, the performance meets the industrial capacity standard of the lithium iron phosphate material, and meanwhile, the lithium iron phosphate material also belongs to a lithium iron phosphate material with better performance.
Comparative example 2
In the comparative example, the lithium iron phosphate/carbon composite material was prepared by wet milling while mixing the lithium salt, the raw material and the carbon source. Firstly, accurately weighing 100g of an abnormal oxidized lithium iron phosphate fine powder raw material sample with extremely low carbon content obtained by crushing, separating and screening, adding lithium hydroxide-lithium carbonate eutectic point mixed lithium salt and lithium fluoride, wherein the molar ratio of the lithium fluoride is 1%, adjusting the molar ratio of lithium to iron in the sample to be 1.1:1, then adding 8g of glucose and 2g of food-grade sucrose, and then pouring the mixture into a ball-milling tank filled with absolute ethyl alcohol for high-speed ball-milling and mixing for 5 hours. Drying, grinding and roller-pair prepressing (the gap between the roller pair is 2 mm), heating to 300 ℃ at the heating rate of 5 ℃/min in the nitrogen protective atmosphere, preserving the heat for 7h, and cooling the material to room temperature to obtain the regenerated lithium iron phosphate/carbon composite materialAnd (5) synthesizing the materials. The carbon content is 1.4 percent and the tap density of the material is 0.93g/cm detected by a carbon-sulfur analyzer3The compaction density of the positive pole piece of the battery core can reach 2.25g/cm3。
The electrical property analysis of the lithium iron phosphate/carbon composite material obtained in the comparative example was performed in the same test manner as in example 1, and the electrical property test results were: the discharge specific capacities corresponding to the multiplying powers of 0.2C, 1C and 2C are 142mAh/g, 134mAh/g and 121mAh/g in sequence, which shows that the dry stirring, grinding and mixing are more favorable for improving the performance of the material in the regeneration process of the lithium iron phosphate/carbon composite material.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (8)
1. The regeneration preparation method of the lithium iron phosphate/carbon composite material is characterized by comprising the following steps of:
s1, collecting sintering powder of the lithium iron phosphate/carbon composite material which is abnormally oxidized in the sintering process, crushing the sintering powder by using an airflow crushing device, and then screening fine powder in a grading manner; carrying out ultrasonic vibration crushing on the fine powder, and simultaneously conveying the powder into a spiral cyclone separator through backfilling induced air flow to realize the separation of the abnormally sintered lithium iron phosphate fine powder from the surface coated carbon;
s2, detecting the content of lithium and iron elements in the abnormally sintered lithium iron phosphate fine powder separated by the S2 by adopting an element analysis method, adding a eutectic point mixed lithium salt to enable the molar ratio of the lithium and the iron elements in the mixture to be 1.1-1.2:1, then adding a reducing carbon source, and stirring and mixing uniformly by a dry method;
and S3, placing the stirred and mixed powder into a high-speed ball mill for full grinding, then compacting by a roller, and placing the compacted powder into an oxygen-free atmosphere for sintering to obtain the regenerated lithium iron phosphate/carbon composite material.
2. The method for regenerating a lithium iron phosphate/carbon composite material according to claim 1, wherein the method comprises the steps of: the jet milling device is one of a flat jet mill, a fluidized bed opposite-jet mill, a circulating pipe jet mill, an opposite-jet mill and a target jet mill.
3. The method for regenerating a lithium iron phosphate/carbon composite material according to claim 1, wherein the method comprises the steps of: the granularity of the fine powder in S1 is required to be D50-300 nm and D100-900 nm.
4. The method for regenerating a lithium iron phosphate/carbon composite material according to claim 1, wherein the method comprises the steps of: the element analysis method is ICP atomic emission spectrometry or atomic absorption spectrometry.
5. The method for regenerating a lithium iron phosphate/carbon composite material according to claim 1, wherein the method comprises the steps of: lithium fluoride is added into the eutectic point mixed lithium salt, and the molar ratio of the lithium fluoride is 1-2%.
6. The method for regenerating a lithium iron phosphate/carbon composite material according to claim 1, wherein the method comprises the steps of: the reducing carbon source is 80% by weight of glucose and 20% by weight of one or more of food-grade sucrose, maltose and fructose.
7. The method for regenerating a lithium iron phosphate/carbon composite material according to claim 1, wherein the method comprises the steps of: and grinding the powder stirred and mixed in the S3 for 3-5 hours by using a high-speed ball mill, and then pre-pressing by using a pair of rollers, wherein the gap between the pair of rollers is 2 mm.
8. The method for regenerating a lithium iron phosphate/carbon composite material according to claim 1, characterized in that: the oxygen-free atmosphere is one or more of nitrogen, argon and helium; the temperature of the anaerobic sintering constant-temperature area is 300-450 ℃, and the heat preservation time is 4-7 hours.
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| CN111017901A (en) * | 2019-12-11 | 2020-04-17 | 合肥国轩电池材料有限公司 | Method for recycling abnormal materials in preparation of lithium iron phosphate positive electrode material |
| CN112614979A (en) * | 2020-12-17 | 2021-04-06 | 华中科技大学 | Secondary carbon-coated lithium iron phosphate and preparation method thereof |
| CN113594460A (en) * | 2021-07-26 | 2021-11-02 | 山东精工电子科技有限公司 | Method for preparing lithium iron phosphate composite material by high-temperature kneading |
| CN113582153A (en) * | 2021-09-30 | 2021-11-02 | 中南大学 | Waste lithium iron phosphate cathode material for repairing and regenerating and repairing and regenerating method thereof |
| CN116443840A (en) * | 2023-03-28 | 2023-07-18 | 合肥国轩高科动力能源有限公司 | Lithium iron phosphate positive electrode material and preparation method thereof |
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