CN115249792A - Positive electrode lithium supplement material, preparation method thereof, positive plate and secondary battery - Google Patents

Positive electrode lithium supplement material, preparation method thereof, positive plate and secondary battery Download PDF

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Publication number
CN115249792A
CN115249792A CN202210809540.9A CN202210809540A CN115249792A CN 115249792 A CN115249792 A CN 115249792A CN 202210809540 A CN202210809540 A CN 202210809540A CN 115249792 A CN115249792 A CN 115249792A
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lithium
positive electrode
supplement material
ferrite
layer
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郑明清
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Zhejiang Liwei Energy Technology Co ltd
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Zhejiang Liwei Energy Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a positive electrode lithium supplement material, a positive plate and a secondary battery. According to the anode lithium supplement material, the surface of lithium ferrite is sequentially coated with the stabilizing layer and the hydrophobic layer, the stabilizing layer can relieve oxygen free radicals generated in the lithium ferrite lithium removal process, the lithium ferrite structure is prevented from being unstable, the hydrophobic layer can prevent lithium in the lithium ferrite from being lost, lithium ions are prevented from being diffused, the material capacity is ensured, and the processing performance is improved.

Description

Positive electrode lithium supplement material, preparation method thereof, positive plate and secondary battery
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a positive electrode lithium supplement material, a preparation method thereof, a positive plate and a secondary battery.
Background
The lithium ion battery is concerned about due to the advantages of high energy density, long cycle life, environmental friendliness, no memory effect and the like, and is widely applied to the fields of 3C digital codes, automobiles and the like. Silicon materials have a high theoretical guest capacity (-4200 mAh/g) and a low discharge voltage (-0.5V vs Li/Li +), and are currently considered to be one of the most promising anode materials to replace graphite. However, the silicon material itself consumes part of the lithium source during the first charging process to form SEI, and some other irreversible losses, which results in low first coulombic efficiency of the silicon material itself. Among many lithium supplement schemes, lithium supplement to the positive electrode is favored due to the characteristics of safety, simplicity, low cost and the like. LFO is increasingly researched and used due to the characteristics of high theoretical specific capacity (867 mAh/g), low cost and the like. However, LFO releases oxygen during charging, which destroys the stability of the structure; in addition, since LFO is generally a high residual base, it is sensitive to water during processing. These become obstacles that limit the widespread use of LFO materials in lithium batteries.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the stabilizing layer and the hydrophobic layer are sequentially coated on the surface of the lithium ferrite, the stabilizing layer can relieve oxygen radicals generated in the lithium ferrite in the lithium removal process, the instability of the lithium ferrite structure is avoided, the loss of lithium in the lithium ferrite can be avoided by the hydrophobic layer, the diffusion of lithium ions is avoided, the material capacity is ensured, and the processing performance is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a positive electrode lithium supplement material comprises lithium ferrite, a stable layer coated on the outer surface of the lithium ferrite and a hydrophobic layer coated on the outer surface of the stable layer.
Preferably, the stabilizing layer is a selenium layer, and the hydrophobic layer is a titanium dioxide layer.
Preferably, the thickness of the stabilizing layer is 1 to 5 μm and the thickness of the hydrophobic layer is 1 to 20 μm.
The second purpose of the invention is: aiming at the defects of the prior art, the preparation method of the anode lithium supplement material is provided, and the anode lithium supplement material is obtained by mixing and heating lithium ferrite and selenium powder to prepare the lithium ferrite, adding the lithium ferrite into a titanium dioxide precipitation solution to mix, centrifuging, drying and heating and calcining.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a positive electrode lithium supplement material comprises the following steps:
step S1, mixing lithium ferrite and selenium powder to obtain an intermediate product, wherein the inner core is formed by coating selenium powder on the outer surface of the lithium ferrite, and the selenium powder is heated to form a stable layer;
and S2, adding tetrabutyl titanate into a solvent for dissolving, adding the intermediate product, stirring, dropwise adding an alkaline solution, centrifuging, cleaning, drying, heating and calcining to obtain the anode lithium supplement material with the outer surface of the intermediate product coated with the hydrophobic layer.
Preferably, the weight parts of the lithium ferrate and the selenium powder in the step S1 are 1-5.
Preferably, the weight part ratio of the tetrabutyl titanate to the intermediate product in the step S2 is 0.1-0.8.
Preferably, the alkaline solution in step S2 is 0.05 to 2ml of ammonia water.
Preferably, the preparation method of the lithium ferrite comprises the following steps: mixing an iron source and a lithium source at the temperature of 500-700 ℃, heating for 10-15 h, raising the temperature to 780-850 ℃, heating for 30-48 h, cooling, and grinding to obtain the lithium ferrite.
Preferably, the molar ratio of the iron source to the lithium source is 1 to 3.
The third purpose of the invention is: aiming at the defects of the prior art, the positive plate comprises the positive lithium supplement material and has good electrochemical performance and structural stability.
In order to achieve the purpose, the invention adopts the following technical scheme:
a positive plate comprises the positive electrode lithium supplement material.
The fourth purpose of the invention is that: aiming at the defects of the prior art, the secondary battery is provided, and has good quality and good cycle performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a secondary battery comprises the positive plate.
Compared with the prior art, the invention has the beneficial effects that: according to the anode lithium supplement material, the surface of lithium ferrite is sequentially coated with the stabilizing layer and the hydrophobic layer, the stabilizing layer can relieve oxygen free radicals generated in the lithium ferrite lithium removal process, the lithium ferrite structure is prevented from being unstable, the hydrophobic layer can prevent lithium in the lithium ferrite from being lost, lithium ions are prevented from being diffused, the capacity of the material is ensured, and the processing performance is improved.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
A positive electrode lithium supplement material comprises lithium ferrite, a stable layer coated on the outer surface of the lithium ferrite and a hydrophobic layer coated on the outer surface of the stable layer.
In addition, the lithium ferrite is usually high in residual alkali and sensitive to water in the processing process, so that the lithium ferrite material is difficult to apply. According to the anode lithium supplement material, the surface of lithium ferrite is sequentially coated with the stabilizing layer and the hydrophobic layer, the stabilizing layer can relieve oxygen free radicals generated in the lithium ferrite lithium removal process, the lithium ferrite structure is prevented from being unstable, the hydrophobic layer can prevent lithium in the lithium ferrite from being lost, lithium ions are prevented from being diffused, the capacity of the material is ensured, and the processing performance is improved.
In some embodiments, the stabilizing layer is a selenium layer and the hydrophobic layer is a titanium dioxide layer. The selenium element is a VIA group element, and can form a stable bonding layer with the lithium ferrite, so that the situation that the lithium ferrite breaks due to unstable structure caused by oxygen release in the charging process is avoided, and the service life of the material is greatly shortened. Similarly, a sulfur layer, preferably selenium layer, can be used to improve the structural stability. The titanium dioxide has titanium-oxygen bonds and is relatively high in polarity, water adsorbed on the surface is dissociated due to polarization, hydroxyl groups are easily formed, and the surface hydroxyl groups can improve the performance of the titanium dioxide as an adsorbent and various monomers, so that convenience is provided for surface modification.
In some embodiments, the stabilizing layer has a thickness of 1 to 5 μm and the hydrophobic layer has a thickness of 1 to 20 μm. Preferably, the thickness of the stabilizing layer is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm. The thickness of the water-repellent layer is 1 μm, 3 μm, 5 μm, 9 μm, 10 μm, 12 μm, 15 μm, 16 μm, 18 μm, or 20 μm.
A preparation method of a positive electrode lithium supplement material comprises the following steps:
step S1, mixing lithium ferrite with selenium powder to obtain an intermediate product, wherein the core is formed by coating selenium powder on the outer surface of the lithium ferrite, and heating the selenium powder to form a stable layer;
and S2, adding tetrabutyl titanate into a solvent for dissolving, adding the intermediate product, stirring, dropwise adding an alkaline solution, centrifuging, cleaning, drying, heating and calcining to obtain the anode lithium supplement material with the outer surface of the intermediate product coated with the hydrophobic layer.
A preparation method of a positive electrode lithium supplement material comprises the steps of mixing and heating lithium ferrite and selenium powder to obtain lithium ferrite, adding the lithium ferrite into titanium dioxide precipitation liquid, mixing, centrifuging, drying, and heating and calcining to obtain the positive electrode lithium supplement material.
Mixing lithium ferrite and selenium powder, heating to obtain an intermediate product Se @ LFO, namely the lithium ferrite coated by a selenium layer, adding the lithium ferrite material coated by the Se @ LFO selenium layer into a titanium dioxide precipitation solution, coating the titanium dioxide precipitation on the surface of the lithium ferrite material coated by the Se @ LFO selenium layer, centrifuging, cleaning, drying, heating and calcining to obtain the anode lithium supplement material. The preparation method of the titanium dioxide precipitation solution comprises the steps of adding tetrabutyl titanate into a solvent for dissolving, and then adding an alkaline solution to fully perform hydrolysis reaction, so as to obtain amorphous titanium dioxide precipitation. Wherein the alkaline solution is 0.2-1.2 mol/L ammonia water solution, and the addition amount is 0.05-10 ml, preferably 0.05-6 ml, 1-5 ml and 2-4 ml.
In some embodiments, the weight parts of the lithium ferrate and the selenium powder in step S1 are 1 to 5. Preferably, the weight parts of the lithium ferrate and the selenium powder are 1-5. Specifically, the weight parts of lithium ferrate and selenium powder are 1.
In some embodiments, the weight ratio of tetrabutyl titanate to the intermediate product in the step S2 is 0.1 to 0.8. The weight portion ratio of the tetrabutyl titanate to the intermediate product is 0.1-0.8.
In some embodiments, the alkaline solution in step S2 is 0.05 to 2ml of ammonia water. The alkaline solution is ammonia water, sodium hydroxide solution, calcium hydroxide solution, specifically, 0.05-2 ml of 0.02-0.5 mol/L ammonia water is used.
In some embodiments, the method for preparing lithium ferrite in step S1 comprises: mixing an iron source and a lithium source at the temperature of 500-700 ℃, heating for 10-15 h, raising the temperature to 780-850 ℃, heating for 30-48 h, cooling, and grinding to obtain the lithium ferrite. The preparation method of the lithium ferrite mixes the iron source and the lithium source, and carries out low-temperature presintering and then heating for high-temperature calcination, and secondary calcination can ensure that the reaction is more sufficient, the formed lithium ferrite has a more stable structure, and the structure is not easy to be unstable due to deoxidation in the charging process.
In some embodiments, the molar ratio of the iron source to the lithium source in step S1 is 1 to 3. The molar ratio of the iron source to the lithium source is 1-3. Specifically, the molar ratio of the iron source to the lithium source is (1).
The positive plate comprises the positive lithium supplement material and has good electrochemical performance and structural stability.
A positive plate comprises the positive lithium supplement material. Specifically, the positive plate comprises a positive current collector and a positive active coating arranged on at least one surface of the positive current collector, wherein the positive active coating comprises the positive lithium supplement material. The positive electrode lithium supplement material has lithium ions and can provide a lithium source for the positive plate, so that the loss of the first charge and discharge and the loss in the circulation process are supplemented.
A secondary battery has good quality and good cycle performance.
A secondary battery comprises the positive plate. Specifically, the secondary battery comprises a negative electrode sheet, a separation film, an electrolyte, a shell and the positive electrode sheet.
The positive electrode current collector is generally a structure or a part for collecting current, and may be any material suitable for use as a positive electrode current collector of a lithium ion battery in the art, for example, the positive electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, an aluminum foil, and the like.
The negative plate comprises a negative current collector and a negative active material layer arranged on the surface of the negative current collector, wherein the negative active material layer comprises a negative active material, and the negative active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming an alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. The negative electrode current collector is generally a structure or a part for collecting current, and the negative electrode current collector may be any material suitable for use as a negative electrode current collector of a lithium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.
The lithium ion battery also comprises electrolyte, and the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte 6 And/or LiBOB; or LiBF used in low-temperature electrolyte 4 、LiBOB、LiPF 6 At least one of; or LiBF used in anti-overcharge electrolyte 4 、LiBOB、LiPF 6 At least one of, liTFSI; may also be LiClO 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of (1). And the organic solvent may be a cyclic carbonate including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. While additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, anti-overcharge additives, control additivesIn electrolyte H 2 At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.
Preferably, the material of casing is one of stainless steel, plastic-aluminum membrane. More preferably, the housing is an aluminum plastic film.
Example 1
(1) LFO is prepared by a high-temperature solid phase method. Mixing nano Fe 2 O 3 And LiOH. H 2 O is mixed and ground according to a molar ratio of 1. Then heating to 600 ℃ at a heating rate of 2 ℃/min and continuing to heat for 12h to perform pre-sintering. Then heating to 800 ℃ at the heating rate of 2 ℃/min and continuing to heat for a certain time of 36h. After the temperature was reduced to room temperature, the LFO material was ground and passed through a 400 mesh standard sieve to obtain particles of uniform size.
(2) And uniformly mixing the LFO and the Se powder obtained in the previous step according to the mass ratio of 1. The mixture was transferred to a tube furnace (Ar) and heated to 250 ℃ at a heating rate of 2 ℃/min and continued for 50min to obtain Se @ LFO.
(3) Tetrabutyl titanate (TBOT, 0.1918 g) was added to 40mL of ethanol and stirred for 1h, after which 6g of the above-mentioned Se @ LFO was added to the mixed solution and stirred for 2h. Next 0.5mL NH 3 ·H 2 O was slowly added to the above solution. Then, the powder obtained by centrifugation was repeatedly washed with anhydrous ethanol and deionized water several times, and vacuum-dried at 120 ℃ for 10 hours to obtain a powder. Finally, heating the mixture for 5 hours in a muffle furnace at 500 ℃ to obtain the nano TiO 2 @Se@LFO。
Example 2
(1) LFO is prepared by a high-temperature solid phase method. Mixing nano Fe 2 O 3 And LiOH. H 2 O is mixed and ground according to a molar ratio of 1. Then heating to 600 ℃ at a heating rate of 2 ℃/min and continuing heating for 12h to perform pre-sintering. Then heating to 800 ℃ at a heating rate of 2 ℃/min and continuing to heat for 32h. After cooling to room temperature, the LFO material was ground and passed through a 400 mesh standard sieve to obtain particles of more uniform size.
(2) And uniformly mixing the LFO and the Se powder obtained in the previous step according to the mass ratio of 1. Transferring the mixture to a tube furnace (Ar), heating to 200-300 deg.C at a heating rate of 2 deg.C/min, and continuously heating for 10-60min to obtain Se @ LFO.
(3) Tetrabutyl titanate (TBOT, 0.1918 g) was added to 40mL ethanol and stirred for 1h, after which a certain amount of 7g of the above Se @ LFO was added to the mixed solution and stirring was continued for 2h. Next 0.2mLNH will be added 3 ·H 2 O was slowly added to the above solution. Then, the powder obtained by centrifugation was repeatedly washed with anhydrous ethanol and deionized water several times, and vacuum-dried at 120 ℃ for 10 hours to obtain a powder. Finally, heating the mixture for 5 hours in a muffle furnace at 500 ℃ to obtain the nano TiO 2 @Se@LFO。
Example 3
(1) LFO is prepared by a high-temperature solid phase method. Mixing nano Fe 2 O 3 And LiOH. H 2 O is mixed and ground according to a certain molar ratio of 1. Then heating to 600 ℃ at a heating rate of 2 ℃/min and continuing to heat for 12h to perform pre-sintering. Then heating to 800 ℃ at the heating rate of 2 ℃/min and continuously heating for a certain time of 32h. After the temperature was reduced to room temperature, the LFO material was ground and passed through a 400 mesh standard sieve to obtain particles of uniform size.
(2) And uniformly mixing the LFO and the Se powder obtained in the previous step according to the mass ratio of 1. The mixture was transferred to a tube furnace (Ar) and heated to 240 ℃ at a heating rate of 2 ℃/min and continued for 10-60min to obtain Se @ LFO.
(3) Tetrabutyl titanate (TBOT, 0.1918 g) was added to 40mL ethanol and stirred for 1h, after which 3g of the above Se @ LFO was added to the mixed solution and stirring was continued for 2h. Next 0.2mL NH 3 ·H 2 O was slowly added to the above solution. Then, the powder obtained by centrifugation was repeatedly washed with anhydrous ethanol and deionized water several times, and vacuum-dried at 120 ℃ for 10 hours to obtain a powder. Finally, heating the mixture for 5 hours in a muffle furnace at 500 ℃ to obtain the nano TiO 2 @Se@LFO。
Example 4
The difference from example 1 is that: in the step S1, the weight parts of lithium ferrate and selenium powder are 2.
The rest is the same as in example 1.
Example 5
The difference from example 1 is that: in the step S1, the weight parts of lithium ferrate and selenium powder are 3.
The rest is the same as in example 1.
Example 6
The difference from example 1 is that: in the step S1, the weight parts of lithium ferrate and selenium powder are 4.
The rest is the same as in example 1.
Example 7
The difference from example 1 is that: the preparation method of the lithium ferrite comprises the following steps: mixing an iron source and a lithium source at 500 ℃, heating for 10 hours, raising the temperature to 780 ℃, heating for 30 hours, cooling, and grinding to obtain lithium ferrite.
The rest is the same as in example 1.
Example 8
The difference from example 1 is that: the preparation method of the lithium ferrite comprises the following steps: mixing an iron source and a lithium source at the temperature of 600 ℃, heating for 12h, raising the temperature to 800 ℃, heating for 35h, cooling, and grinding to obtain the lithium ferrite.
The rest was the same as in example 1.
Example 9
The difference from example 1 is that: the preparation method of the lithium ferrite comprises the following steps: mixing an iron source and a lithium source at 680 ℃, heating for 15h, raising the temperature to 830 ℃, heating for 40h, cooling, and grinding to obtain lithium ferrite.
The rest is the same as in example 1.
Example 10
The difference from example 1 is that: the preparation method of the lithium ferrite comprises the following steps: mixing an iron source and a lithium source at the temperature of 600 ℃, heating for 14h, raising the temperature to 830 ℃, heating for 45h, cooling, and grinding to obtain the lithium ferrite.
The rest is the same as in example 1.
Comparative example 1
Using Li 4 FeO 4 Can be used as a lithium supplement material.
The materials prepared in examples 1-10 and comparative example 1 were subjected to the first coulombic efficiency and gram volume test, and the test results are reported in table 1.
TABLE 1
Item ICE Gram capacity (mAh/g)
Example 1 90.0 184
Example 2 89.6 183.8
Example 3 89.0 182.8
Example 4 87 183.6
Example 5 89 183
Example 6 86 182
Example 7 85 185
Example 8 87 184
Example 9 86 186
Example 10 85 182
Comparative example 1 53 164
1. Electrical properties: the lithium ion batteries of examples 1-10 and comparative example 1 were tested for their electrochemical performance at 3C buck charge/0.7C discharge cycles, rate charge (2C discharge to 3V) and reported in table 2.
TABLE 2
Figure BDA0003740083720000091
Figure BDA0003740083720000101
As can be seen from tables 1 and 2, the positive electrode lithium supplement material prepared according to the present invention has better performance and is significantly improved compared to the lithium supplement material of comparative example 1. Compared with the examples 1 and 4-6, the prepared positive electrode lithium supplement material has better performance when the weight parts of the lithium ferrite and the selenium powder in the step S1 are set to be 1. The lithium ferrite is more stable in structure because a certain amount of selenium powder is coated on the outer surface of the lithium ferrite to form a stable layer with a certain coating rate, but the selenium powder can be combined with oxygen radicals released during lithium removal to form a stable structure in the charging process, so that the phenomenon that the structure is unstable and cracked due to the lithium removal is avoided. And a certain weight part ratio of lithium ferrate to selenium powder is set, so that the coating rate of the stable layer is higher, the stability is better, and the prepared secondary battery has better first coulombic efficiency, higher gram capacity, higher cycle capacity and higher rate charge capacity.
The comparison of the examples 1 and 7-10 shows that when the following method parameters are used in the preparation method of the lithium ferrite, the prepared lithium ferrite has better effect when applied to a positive electrode lithium supplement material and a battery. Mixing an iron source and a lithium source at the temperature of 600 ℃, heating for 12 hours, raising the temperature to 800 ℃, heating for 35 hours, cooling, and grinding to obtain lithium ferrite. The obtained secondary battery has good coulombic efficiency for the first time, up to 90 percent, high gram capacity, up to 184mAh/g, higher circulating capacity retention rate, circulating capacity retention rate up to 82.5 percent and multiplying power charging capacity retention rate, up to 94.1 percent.
Variations and modifications to the above-described embodiments may become apparent to those skilled in the art to which the invention pertains based upon the disclosure and teachings of the above specification. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (11)

1. The positive electrode lithium supplement material is characterized by comprising lithium ferrite, a stable layer coated on the outer surface of the lithium ferrite and a hydrophobic layer coated on the outer surface of the stable layer.
2. The positive electrode lithium supplement material according to claim 1, wherein the stabilizing layer is a selenium layer and the hydrophobic layer is a titanium dioxide layer.
3. The positive electrode lithium supplement material according to claim 1, wherein the stabilizing layer has a thickness of 1 to 5 μm, and the hydrophobic layer has a thickness of 1 to 20 μm.
4. The preparation method of the positive electrode lithium supplement material according to any one of claims 1 to 3, characterized by comprising the steps of:
step S1, mixing lithium ferrite and selenium powder to obtain an intermediate product, wherein the inner core is formed by coating selenium powder on the outer surface of the lithium ferrite, and the selenium powder is heated to form a stable layer;
and S2, adding tetrabutyl titanate into a solvent to dissolve, adding the intermediate product, stirring, dropwise adding an alkaline solution, centrifuging, cleaning, drying, heating and calcining to obtain the anode lithium supplement material with the outer surface of the intermediate product coated with the hydrophobic layer.
5. The method for preparing the positive electrode lithium supplement material according to claim 4, wherein the weight parts of the lithium ferrate and the selenium powder in the step S1 are 1-5.
6. The method for preparing the lithium supplement material for the positive electrode according to claim 4, wherein the weight part ratio of the tetrabutyl titanate to the intermediate product in the step S2 is 0.1-0.8.
7. The method for preparing a lithium supplement material for a positive electrode according to claim 4, wherein the alkaline solution in the step S2 is 0.05 to 2ml of ammonia water.
8. The method for preparing a lithium supplement material for a positive electrode according to claim 4, wherein the method for preparing lithium ferrite comprises the following steps: mixing an iron source and a lithium source at the temperature of 500-700 ℃, heating for 10-15 h, raising the temperature to 780-850 ℃, heating for 30-48 h, cooling, and grinding to obtain the lithium ferrite.
9. The method for preparing the positive electrode lithium supplement material according to claim 8, wherein the molar ratio of the iron source to the lithium source is 1-3.
10. A positive electrode sheet comprising the positive electrode lithium supplement material according to any one of claims 1 to 3.
11. A secondary battery comprising the positive electrode sheet according to claim 10.
CN202210809540.9A 2022-07-11 2022-07-11 Positive electrode lithium supplement material, preparation method thereof, positive plate and secondary battery Pending CN115249792A (en)

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* Cited by examiner, † Cited by third party
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CN116230842A (en) * 2022-12-12 2023-06-06 湖北万润新能源科技股份有限公司 Preparation method of lithium supplementing agent

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116230842A (en) * 2022-12-12 2023-06-06 湖北万润新能源科技股份有限公司 Preparation method of lithium supplementing agent
CN116230842B (en) * 2022-12-12 2024-04-02 湖北万润新能源科技股份有限公司 Preparation method of lithium supplementing agent

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