CN110459762B - Mn-doped lithium ferrate, lithium supplement positive electrode material, and preparation and application thereof - Google Patents
Mn-doped lithium ferrate, lithium supplement positive electrode material, and preparation and application thereof Download PDFInfo
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- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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Abstract
The invention belongs to the field of lithium ion battery materials, and particularly discloses an application of Mn-doped lithium ferrate, which is used as a lithium supplement additive to be added into a positive active material for preparing a lithium supplement positive material of a lithium ion battery; the chemical formula of the Mn-doped lithium ferrate is Li5Fe1‑xMnxO4(ii) a Wherein x is 0.05-0.1. The invention also provides a preparation method of Mn-doped lithium ferrate adopted in the application method, which comprises the steps of ball-milling an iron source, a manganese source and a lithium source in stoichiometric ratio in a surfactant solution, and then spray-drying to obtain a precursor; and sintering the precursor at 600-900 ℃ in a protective atmosphere to obtain the Mn-doped lithium ferrate. The invention also provides the lithium-supplement anode material and application of the anode material in a lithium ion battery. The invention discovers that the lithium supplement additive and the positive active material have cooperativity, and in addition, the invention also provides a preparation method which is simple to operate, short in preparation period and high in product activity.
Description
Technical Field
The invention belongs to the field of energy storage devices, and particularly relates to a lithium supplement agent, a preparation method of a lithium ion battery and the lithium ion battery.
Background
Lithium Ion Batteries (LIBs) currently have the most promising and fastest-developing high-efficiency secondary batteries, and have the advantages of higher specific energy, low self-discharge, good cycle performance, no memory effect and the like.
Li + in the lithium ion battery is completely from a positive electrode material, and a negative electrode is generally made of a graphite material. When the battery is charged for the first time, the surface of the negative electrode of the lithium ion battery consumes Li + to form an SEI film, so that the problem of Initial Capacity Loss (ICL) is caused, and the ICL of the lithium ion battery of the graphite negative electrode is about 7-10%. High-capacity silicon cathode materials are gradually applied to lithium ion batteries, but the ICL of the silicon cathode is as high as 50-70%. Therefore, it is of great significance to develop a simple and efficient lithium supplement technology.
The current lithium supplement scheme mainly comprises negative electrode lithium supplement, wherein the current lithium supplement scheme can be divided into a primary battery lithium supplement technology and an auxiliary anode lithium supplement technology. However, the research results show that the existing lithium supplement technology has the following problems: the lithium-inserting current of the original battery for lithium supplement is uncontrollable, the requirement on the production process is extremely high, and potential safety hazards exist; the auxiliary anode lithium supplement is difficult to realize continuous production and has potential safety hazard easily. In recent years, researchers at home and abroad gradually put the line of sight on lithium supplement of the positive electrode. The positive pole lithium supplement is characterized in that a positive pole material with high lithium content is selected in addition to a traditional positive pole material, and is mixed with the traditional positive pole material according to a certain proportion to be used as a brand new positive pole material for assembling the battery. During the first charge and discharge process, excessive Li released from high-Li positive electrode material as additive+Will fill in the irreversible Li produced at the cathode+And thus the ICL of the entire battery is reduced. Compared with the negative electrode lithium supplement technology, the positive electrode lithium supplement is safer and easy to industrialize, the existing equipment and flow of a factory do not need to be changed, and the method is very promising lithium supplement technology. However, the high-lithium positive electrode material required by the positive electrode lithium supplement still needs further research, namely the core of the positive electrode lithium supplement technology lies in finding a positive electrode material which has high lithium content, can release lithium to the maximum extent under the charging and discharging conditions of the existing battery, has low cost and is simple to prepare
Li5FeO4The lithium-rich transition metal oxide with an inverse fluorite structure has very high specific capacity which can reach 867mAh/g, has very low first charge-discharge efficiency, can remove lithium to the maximum extent and supplement ICL on a negative electrode, so that Li5FeO4Has great application potential in the field of solving the problem of the ICL of the lithium ion battery. However, the preparation of conventional Li has been reported so far5FeO4The sintering process conditions are harsh, and the synthesized Li5FeO4Large particle size, low electron conductivity, influence on Li5FeO4And its applications.
Disclosure of Invention
To overcome the disadvantages and drawbacks of the prior art, a first object of the present invention is to provide a Mn-doped lithium ferrate (also referred to as Mn-doped Li in the present invention)5FeO4Lithium supplement agent Li5Fe1-xMnxO4Or Li5Fe1-xMnxO4Lithium supplement agent) as an additive to the existing positive electrode active material, aiming at synergistically improving the electrical properties.
The second purpose of the invention is to provide a preparation method of Mn-doped lithium ferrate, which belongs to the application range and aims to obviously shorten the preparation period and prepare Mn-doped lithium ferrate with excellent performance.
The third purpose of the invention is to provide a lithium supplement cathode material containing the Mn-doped lithium ferrate, which aims to obviously improve the electrical property of the cathode material obtained by compounding through the cooperation of the additive and the cathode active material.
The fourth purpose of the invention is to provide a preparation method of the lithium supplement cathode material.
The fifth purpose of the invention is to provide an application of the lithium supplement cathode material in the preparation of a lithium ion battery.
A sixth object of the present invention is to provide a lithium ion battery to which the lithium-supplementing positive electrode material is added.
The application of Mn-doped lithium ferrate is used as a lithium supplement additive, is added into a positive active material, and is used for preparing a lithium supplement positive material of a lithium ion battery;
the chemical formula of the Mn-doped lithium ferrate is Li5Fe1-xMnxO4(ii) a Wherein x is 0.05-0.1.
Mn in the Mn-doped lithium ferrate partially replaces iron in a lithium ferrate crystal lattice, and the lithium ferrate crystal lattice has an inverted fluorite structure. The inventor innovatively finds that the Mn-doped lithium ferrate material and the positive active material are used together, so that the Mn-doped lithium ferrate material has good cooperativity, can realize the positive lithium supplement effect, is beneficial to forming an SEI film on a negative electrode, improves the stability of the material, and not only can obviously cooperate to improve the electrical property and improve the first charge-discharge coulombic efficiency.
Preferably, the Mn-doped lithium ferrate has a particle size of less than 10 mu m and a specific surface area of 200-800 m2·g-1。
The positive active material may be an existing conventional positive active material.
Preferably, the positive active material is LiCoO2、LiFePO4And at least one of NCM ternary material.
Preferably, in the application, the percentage content of Mn-doped lithium ferrate in the lithium supplement positive electrode material is 2-15 wt%.
Researches show that the mass ratio of the Mn-doped lithium ferrate to the positive active material is controlled in the range, so that the synergistic effect of the Mn-doped lithium ferrate and the positive active material can be further improved, the electrical property is further improved, and the first charge-discharge coulombic efficiency is improved.
The application of the invention, the lithium-supplement positive electrode material, comprises other components which are allowed to be added in the positive electrode material, such as a conductive agent, a binder, a solvent and the like, besides the lithium supplement additive and the positive electrode active material.
Preferably, in the application of the invention, the lithium supplement additive, the positive electrode active material, the conductive agent, the binder and the solvent are slurried to prepare positive electrode slurry, the positive electrode slurry is coated on the surface of the positive electrode current collector, and is cured and compounded on the surface of the positive electrode current collector to obtain the lithium supplement positive electrode material.
Preferably, in the lithium supplement cathode material, the percentage content of the lithium supplement additive is 2-15 wt%.
The conductive agent can be a material which can be recognized in the industry and can be used for the positive electrode and has conductive performance; for example, at least one of acetylene black and ketjen black.
Preferably, in the lithium-supplement cathode material, the percentage content of the conductive agent is 5-10 wt%.
The binder can be a material which can be used for mutually binding the positive pole components and can be recognized in the industry; for example, at least one of PVDF and PTFE may be used.
Preferably, in the lithium-supplement cathode material, the percentage content of the binder is 5-10 wt%.
In the application scope, the invention also provides a preparation method of the Mn-doped lithium ferrate, which comprises the steps of ball-milling an iron source, a manganese source and a lithium source with stoichiometric ratio (the ratio of Li, Fe and Mn elements is 5: 1-x: x) in a surfactant solution, and then spray-drying to obtain a precursor; and sintering the precursor at 600-900 ℃ in a protective atmosphere to obtain the Mn-doped lithium ferrate.
According to the invention, the raw materials are innovatively subjected to wet ball milling in the solution atmosphere of the surfactant to fully mix and activate the materials, and then the spray drying and the sintering at the temperature are matched, so that the lithium supplement additive can be efficiently prepared, the preparation time is obviously shortened, and the performance of the obtained lithium supplement additive is also obviously improved.
Preferably, the iron source is Fe2O3、Fe2SO4、Fe(NO3)3·2H2O、Fe(OH)3At least one of (1).
More preferably, the iron source is a water-insoluble material, and more preferably Fe2O3。
Preferably, the manganese source is MnC2O4·2H2O、MnCO3、Mn(OH)2At least one of MnO and MnO; further preferably MnC2O4·2H2O、MnCO3、Mn(OH)2At least one of (1).
Preferably, the lithium source is Li2CO3、LiF、Li3PO4、Li2C2O4At least one of; further preferred is Li2CO3、LiF、Li2C2O4At least one of (1).
In the present invention, the surfactant may be at least one of a cationic surfactant, an anionic surfactant, and a neutral surfactant.
Preferably, the surfactant comprises one or more of dodecyl (hexa) alkyltrimethyl ammonium bromide, stearic acid, sodium dodecyl benzene sulfonate and polyvinylpyrrolidone.
Preferably, the surfactant is 2 to 10wt% of the iron source.
According to the preparation method, wet ball milling is carried out in the surfactant atmosphere, and materials can be fully activated by utilizing the physical and chemical dual activation effects of the ball milling and the surfactant, so that the preparation time is shortened, and the performance of the obtained lithium supplement additive is improved.
Preferably, the ball milling speed is 200 to 400 r/min.
Preferably, the ball milling is carried out for 1-3 h.
Preferably, the solution after ball milling is spray-dried at 160 to 200 ℃.
The feeding speed in the spray drying process is 10-30 ml/min.
In the invention, spray drying is carried out to obtain a precursor, and the precursor contains fully activated materials and a surfactant. According to the invention, the precursor is innovatively sintered at the temperature, so that a good sintering effect can be ensured under the condition of obviously shortening the sintering time, and the performance of the lithium supplement additive obtained by sintering is improved.
Preferably, the sintering temperature is 650-850 ℃.
Further preferably, the sintering temperature is 750-850 ℃. At the preferred sintering temperature, the electrochemical performance of the prepared material can be further improved.
Preferably, the sintering time is 24-48 h. Under the preparation method, the sintering time can be obviously shortened, and the performance of the obtained material can be improved.
A more preferable preparation method of Mn-doped lithium ferrate comprises the following steps:
(1) weighing a certain proportion of Fe2O3、MnC2O4·2H2O and Li2CO3Dispersed in a solution containing Fe2O3Ball milling is carried out for 1-3 h in deionized water with 2-10% of surfactant by mass, and the ball milling speed is 200-400 r/min;
(2) spray drying the slurry obtained in the step (1) at 160-200 ℃ to obtain a uniformly mixed precursor, wherein the feeding speed is 10-30 ml/min;
(3) and (3) placing the precursor obtained in the step (2) in an inert atmosphere, and sintering at 600-900 ℃ for 24-48 h. After cooling, uniform Li is obtained5Fe1-xMnxO4。
Preferably, in (1), the Fe2O3And MnC2O4·2H2The molar ratio of O is 4.5-9.5: 1, and the surfactant comprises: one or more of dodecyl (hexa) alkyl trimethyl ammonium bromide, stearic acid, sodium dodecyl benzene sulfonate and polyvinylpyrrolidone, wherein the addition amount of the surfactant is Fe2O32 to 10wt% of the total amount of the catalyst.
(3) In (b), Li of the physical and chemical properties of the precursor5Fe1-xMnxO4Has a great influence. By adjusting the reaction conditions, the agglomeration of the product is reduced, the product dispersibility can be improved, and the specific surface area of the precursor is increased.
The invention also discloses a lithium-supplement cathode material which comprises the following components in parts by weight: the Mn-doped lithium ferrate and the positive electrode active material are contained.
Preferably, in the lithium supplement cathode material, the percentage content of the Mn-doped lithium ferrate in the cathode material is 5-15 wt%.
Preferably, in the lithium-supplementing cathode material, the cathode active material is LiCoO2、LiFePO4And at least one of NCM ternary material.
Preferably, the lithium-supplement cathode material further comprises a conductive agent and a binder; wherein the content of the conductive agent is 5-10%; the content of the binder is 5-10%.
The invention also provides a preparation method of the lithium supplement positive electrode material, which comprises the steps of firstly preparing Mn-doped lithium ferrate by using the method, and then preparing the lithium supplement positive electrode material by using the Mn-doped lithium ferrate, the positive electrode active material and additive components (such as a conductive agent and a binding agent) which are allowed to be added for preparing the positive electrode material.
The invention also discloses an application of the lithium-supplement cathode material: the method is used for preparing the anode piece of the lithium ion battery.
Preferably, the lithium-supplement positive electrode material is applied to the preparation of a lithium ion battery by using the prepared positive electrode piece.
Preferably, the lithium ion battery is obtained by assembling the positive pole piece, the diaphragm, the negative pole piece and the electrolyte.
The application of the lithium-supplement cathode material specifically comprises the following steps: a positive electrode active material, Li5Fe1-xMnxO4The lithium supplement agent, the conductive agent and the binder are uniformly mixed and then subjected to subsequent treatment to obtain a positive pole piece of the lithium ion battery, the negative active material, the conductive agent and the binder are uniformly mixed and then subjected to subsequent treatment to obtain a negative pole piece of the lithium ion battery, and the positive pole piece and the negative pole piece are assembled and then subjected to activation treatment to realize lithium supplement of the negative pole piece to obtain the lithium ion battery.
Preferably, the negative active material is one or more of graphite, hard carbon and silicon carbon material.
Preferably, in the positive electrode plate, the Mn is doped with Li5FeO4Lithium supplement agent Li5Fe1-xMnxO4The mass of the conductive agent is 2-15% of the total mass of the lithium-supplement positive electrode material, and the mass of the conductive agent and the binder is 5-10% of the mass of the lithium-supplement positive electrode material; in the negative pole piece, the total mass of the conductive agent and the binder is 5-10% of the mass of the negative pole material.
Preferably, the Li5Fe1-xMnxO4The first charge capacity of 450 to 700 mAh.g-1The first charge-discharge efficiency is 1-10%, the particle size is less than 10 mu m, and the specific surface area is 200-800 m2·g-1。
The lithium supplement anode material is applied to lithium supplement treatment of an assembled lithium ion battery, preferably, the lithium supplement treatment is performed through one-time charge-discharge circulation, the first charge adopts 0.02-0.1C for constant-current or constant-voltage charge, the cut-off voltage is 4.0-4.5V, the first discharge adopts 0.02-0.1C for constant-current discharge, and the cut-off voltage is 1.5-2.0V. The lithium in the material can be completely removed by adopting small current during charging, and the material structure can be damaged by adopting large current during discharging, so that the lithium can not be removed.
The invention also provides a lithium ion battery assembled by the lithium-supplement cathode material as a general technical concept. The first charge-discharge coulombic efficiency of the lithium ion battery is 90-99%.
Compared with the prior art, the invention has the advantages that:
1. the invention utilizes high-lithium material Li5Fe1-xMnxO4The lithium is supplemented to the negative electrode of the lithium battery, so that the problem of capacity loss of the battery in the first charge-discharge process can be effectively solved, and the energy density and the cycle performance of the whole battery are improved.
2. The present invention is directed to the preparation of conventional Li5FeO4The sintering process conditions are harsh, and the synthesized Li5FeO4Large grain size, low electronic conductivity and the like, and the Mn doping is utilized to effectively solve the problems, and the synthesized Li5Fe1-xMnxO4The method has loose requirement on the environment, can be coated together with the prior anode material, and has simple process, easy control and low cost.
3. The invention controls Li5Fe1-xMnxO4The obtained Li has higher specific capacity and lower reversible capacity5Fe1-xMnxO4. Meanwhile, the material has smaller particle size and high specific surface area which can be active ionsThe effect of (a) provides more active sites.
Detailed Description
In order to facilitate an understanding of the present invention, the present invention will be described more fully and in detail with reference to the preferred embodiments, but the scope of the present invention is not limited to the specific embodiments described below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
mn-doped Li5FeO4Lithium supplement agent Li5Fe1-xMnxO4The preparation method of the lithium ion battery for lithium supplement comprises the following steps:
1、Li5Fe1-xMnxO4the preparation of (1):
(1) mixing Fe2O3、MnC2O4·2H2O、Li2CO3Dispersed in the solution containing dodecyl (hexa) alkyl trimethyl ammonium bromide (Fe is dodecyl (hexa) alkyl trimethyl ammonium bromide) according to the mol ratio of 4.5: 1: 252O32 percent of the mass) of the raw materials in deionized water, and ball-milling for 1h at the ball-milling speed of 200 r/min;
(2) spray drying the slurry obtained in the step (1) at 160 ℃ to obtain a uniformly mixed precursor, wherein the feeding speed is 30 ml/min;
(3) placing the precursor obtained in the step (2) in an inert atmosphere, sintering for 24h at 650 ℃, and cooling to obtain the precursor with the first charge capacity of 460 mAh.g-1The first charge-discharge efficiency is 10%, the particle size is 9 μm, and the specific surface area is 240m2·g-1Li of (2)5Fe1-xMnxO4。
2. Subjecting LiCoO to condensation2(65wt％)、Li5Fe1-xMnxO4And (15 wt%), Super P (10 wt%) and PVDF (10 wt%) are uniformly mixed, and then the positive pole piece is obtained through size mixing, coating, drying and rolling.
3. And uniformly mixing graphite (90 wt%), Super P (5 wt%) and PVDF (5 wt%), and then carrying out size mixing, coating, drying and rolling to obtain the negative pole piece.
4. And assembling the positive and negative pole pieces to obtain the lithium ion battery, and realizing lithium supplement of the negative pole material in the first charge-discharge cycle. Wherein the first charge-discharge cycle conditions are as follows:
table 1: first charge-discharge cycle conditions in example 1:
through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the example is 92.2%.
Example 2:
mn-doped Li5FeO4Lithium supplement agent Li5Fe1-xMnxO4The preparation method of the lithium ion battery for lithium supplement comprises the following steps:
1、Li5Fe1-xMnxO4the preparation of (1):
(1) mixing Fe2O3、MnC2O4·2H2O、Li2CO3Dispersed in stearic acid (the stearic acid is Fe) according to a molar ratio of 5.5: 1: 252O34 percent of the mass) of the raw materials in deionized water for ball milling for 2 hours, wherein the ball milling speed is 250 r/min;
(2) spray drying the slurry obtained in the step (1) at 170 ℃ to obtain a uniformly mixed precursor, wherein the feeding speed is 25 ml/min;
(3) subjecting the precursor obtained in step (2)Sintering the precursor in an inert atmosphere at 700 ℃ for 36h, and cooling to obtain the precursor with the first charge capacity of 550mAh g-1The first charge-discharge efficiency is 9%, the particle size is 7 μm, and the specific surface area is 480m2·g-1Li of (2)5Fe1-xMnxO4。
2. Subjecting LiCoO to condensation2(70wt％)、Li5Fe1-xMnxO4And (10 wt%), Super P (10 wt%) and PVDF (10 wt%) are uniformly mixed, and then the positive pole piece is obtained through size mixing, coating, drying and rolling.
3. And uniformly mixing graphite (90 wt%), Super P (5 wt%) and PVDF (5 wt%), and then carrying out size mixing, coating, drying and rolling to obtain the negative pole piece.
4. And assembling the positive and negative pole pieces to obtain the lithium ion battery, and realizing lithium supplement of the negative pole material in the first charge-discharge cycle. Wherein the first charge-discharge cycle conditions are as follows:
table 2: first charge-discharge cycle conditions in example 2:
through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the example is 93.3%.
Example 3:
mn-doped Li5FeO4Lithium supplement agent Li5Fe1-xMnxO4The preparation method of the lithium ion battery for lithium supplement comprises the following steps:
1、Li5Fe1-xMnxO4the preparation of (1):
(1) mixing Fe2O3、MnC2O4·2H2O、Li2CO3Dispersed in stearic acid (stearic acid is Fe) according to the mol ratio of 6.5: 1: 252O36 percent of the mass) of the raw materials in deionized water for ball milling for 3 hours, wherein the ball milling speed is 300 r/min; (ii) a
(2) Spray drying the slurry obtained in the step (1) at 180 ℃ to obtain a uniformly mixed precursor, wherein the feeding speed is 20 ml/min;
(3) placing the precursor obtained in the step (2) in an inert atmosphere, sintering at 750 ℃ for 48h, and cooling to obtain the precursor with the first charge capacity of 620mAh g-1The first charge-discharge efficiency is 7%, the particle size is 5 μm, and the specific surface area is 550m2·g-1Li of (2)5Fe1-xMnxO4。
2. Subjecting LiCoO to condensation2(75wt％)、Li5Fe1-xMnxO4(5 wt%), Super P (10 wt%) and PVDF (10 wt%) are uniformly mixed, and then the positive pole piece is obtained through size mixing, coating, drying and rolling.
3. And uniformly mixing graphite (90 wt%), Super P (5 wt%) and PVDF (5 wt%), and then carrying out size mixing, coating, drying and rolling to obtain the negative pole piece.
4. And assembling the positive and negative pole pieces to obtain the lithium ion battery, and realizing lithium supplement of the negative pole material in the first charge-discharge cycle. Wherein the first charge-discharge cycle conditions are as follows:
table 3: first charge-discharge cycle conditions in example 3:
through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the example is 93.7%.
Example 4:
mn-doped Li5FeO4Lithium supplement agent Li5Fe1-xMnxO4The preparation method of the lithium ion battery for lithium supplement comprises the following steps:
1、Li5Fe1-xMnxO4the preparation of (1):
(1) mixing Fe2O3、MnC2O4·2H2O、Li2CO3Dispersing in sodium dodecyl benzene sulfonate (sodium dodecyl benzene sulfonate is Fe) according to the mol ratio of 7.5: 1: 252O38 percent of the mass) of the raw materials in deionized water for ball milling for 4 hours, wherein the ball milling speed is 350 r/min; (ii) a
(2) Spray drying the slurry obtained in the step (1) at 190 ℃ to obtain a uniformly mixed precursor, wherein the feeding speed is 15 ml/min;
(3) placing the precursor obtained in the step (2) in an inert atmosphere, sintering for 36h at 850 ℃, and cooling to obtain the precursor with the first charge capacity of 650 mAh.g-1The first charge-discharge efficiency is 7%, the particle size is 6 μm, and the specific surface area is 670m2·g-1Li of (2)5Fe1-xMnxO4。
2. Subjecting LiCoO to condensation2(75wt％)、Li5Fe1-xMnxO4(5 wt%), Super P (10 wt%) and PVDF (10 wt%) are uniformly mixed, and then the positive pole piece is obtained through size mixing, coating, drying and rolling.
3. And uniformly mixing graphite (90 wt%), Super P (5 wt%) and PVDF (5 wt%), and then carrying out size mixing, coating, drying and rolling to obtain the negative pole piece.
4. And assembling the positive and negative pole pieces to obtain the lithium ion battery, and realizing lithium supplement of the negative pole material in the first charge-discharge cycle. Wherein the first charge-discharge cycle conditions are as follows:
table 4: first charge-discharge cycle conditions in example 4:
the first charge-discharge efficiency of the lithium ion battery assembled in the example was determined to be 94.1%.
Example 5:
mn-doped Li5FeO4Lithium supplement agent Li5Fe1-xMnxO4The preparation method of the lithium ion battery for lithium supplement comprises the following steps:
1、Li5Fe1-xMnxO4the preparation of (1):
(1) mixing Fe2O3、MnC2O4·2H2O、Li2CO3Dispersed in polyvinylpyrrolidone (polyvinylpyrrolidone is Fe) according to the molar ratio of 8.5: 1: 452O310% of the mass) of the raw materials in deionized water, and ball-milling for 5 hours at the ball-milling speed of 400 r/min; (ii) a
(2) Spray drying the slurry obtained in the step (1) at 200 ℃ to obtain a uniformly mixed precursor, wherein the feeding speed is 10 ml/min;
(3) placing the precursor obtained in the step (2) in an inert atmosphere, sintering for 48h at 850 ℃, and cooling to obtain the precursor with the first charge capacity of 690 mAh.g-1The first charge-discharge efficiency is 5%, the particle size is 4 μm, and the specific surface area is 730m2·g-1Li of (2)5Fe1-xMnxO4。
2. Subjecting LiCoO to condensation2(75wt％)、Li5Fe1-xMnxO4(5 wt%), Super P (10 wt%) and PVDF (10 wt%) are uniformly mixed, and then the positive pole piece is obtained through size mixing, coating, drying and rolling.
3. And uniformly mixing graphite (90 wt%), Super P (5 wt%) and PVDF (5 wt%), and then carrying out size mixing, coating, drying and rolling to obtain the negative pole piece.
4. And assembling the positive and negative pole pieces to obtain the lithium ion battery, and realizing lithium supplement of the negative pole material in the first charge-discharge cycle. Wherein the first charge-discharge cycle conditions are as follows:
table 5: first charge-discharge cycle conditions in example 5:
through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the example is 94.8%.
Comparative example 1:
compared with example 1, the difference is only, in 2, LiCoO280 wt% of Li5Fe1-xMnxO40wt percent of the Super P, 10wt percent of the Super P and 10wt percent of the PVDF are evenly mixed, and then are subjected to size mixing, coating, drying,And rolling to obtain the positive pole piece.
Through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the comparative example is 81.7%. Since no Li is added5Fe1-xMnxO4，LiCoO2The Li + in the graphite cathode is consumed to some extent, so that the first charge-discharge efficiency is not high.
Comparative example 2:
compared with example 1, the difference is only, in 2, LiCoO255 wt% of Li5Fe1-xMnxO4(25 wt%), Super P (10 wt%) and PVDF (10 wt%) are uniformly mixed, and then the positive pole piece is obtained through size mixing, coating, drying and rolling.
Through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the comparative example is 80.6%. Due to the additive Li5Fe1-xMnxO4The first charge-discharge efficiency is very low, and when the addition amount of the lithium ion battery is increased, the key factor limiting the first charge-discharge efficiency of the whole battery is converted from a negative electrode to a positive electrode.
Comparative example 3:
compared with example 1, the difference is only, in 2, LiCoO278 wt% Li5Fe1-xMnxO4(2 wt%), Super P (10 wt%) and PVDF (10 wt%) are uniformly mixed, and then the positive pole piece is obtained through size mixing, coating, drying and rolling.
Through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the comparative example is 83.9%. Due to the additive Li5Fe1-xMnxO4The amount is small, so that the more discharged Li + is not enough to supplement ICL on the graphite cathode, and therefore the first charge-discharge efficiency of the battery is not obviously improved.
Comparative example 4:
the only difference compared to example 1 is that in step (1), no ball milling is used, but mechanical stirring is used to mix the raw materials. Through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the comparative example is 88.6%. The ball milling is matched with the surfactant, so that the raw materials can be fully and synergistically activated, and the obtained product has higher activity, so that the lithium supplementing effect of the additive obtained by adopting the mechanical stirring method in the comparative example is not good as that of example 1.
Comparative example 5:
the only difference compared to example 1 is that in step (1), no surfactant was used in the ball milling. Through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the comparative example is 89.4%. The ball-milled product obtained by adopting the surfactant has higher activity, so the lithium supplementing effect of the additive obtained by adopting the method of the comparative example is not as good as that of the additive obtained by adopting the method of the comparative example 1.
Comparative example 6:
the only difference compared to example 1 is that in step (3), the sintering temperature was 500 ℃. Through determination, the first charge-discharge efficiency of the lithium ion battery assembled in the comparative example is 80.4%. XRD detection shows that the additive Li is not synthesized5Fe1-xMnxO4。
Claims (9)
1. The application of the Mn-doped lithium ferrate is characterized in that the Mn-doped lithium ferrate is used as a lithium supplement additive, the lithium supplement additive, a positive electrode active material, a conductive agent, a binder and a solvent are slurried to prepare positive electrode slurry, the positive electrode slurry is coated on the surface of a positive electrode current collector and is cured, and the lithium supplement positive electrode material is obtained by compounding on the surface of the positive electrode current collector;
the chemical formula of the Mn-doped lithium ferrate is Li5Fe1-xMnxO4(ii) a Wherein x is 0.05-0.1;
the Mn-doped lithium ferrate is prepared by the following steps: ball-milling an iron source, a manganese source and a lithium source in a solution containing a surfactant, and then spray-drying to obtain a precursor; sintering the precursor at 600-900 ℃ in a protective atmosphere to prepare the Mn-doped lithium ferrate;
the iron source is Fe2O3(ii) a The manganese source is MnC2O4·2H2O；Fe2O3And MnC2O4·2H2The molar ratio of O is 4.5-9.5: 1;
carrying out spray drying on the ball-milled solution at 160-200 ℃;
in the lithium supplement anode material, the percentage content of Mn-doped lithium ferrate in the lithium supplement anode material is 5-15 wt%.
2. The use of a Mn-doped lithium ferrate according to claim 1, wherein the positive active material is LiCoO2、LiFePO4And at least one of NCM ternary material.
3. The application of the Mn-doped lithium ferrate according to claim 1, wherein in the lithium supplement positive electrode material, the percentage of the conductive agent is 5-10 wt%;
the percentage content of the binder is 5-10 wt%.
4. The use of a Mn-doped lithium ferrate according to claim 1, wherein the surfactant comprises one or more of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, stearic acid, sodium dodecylbenzenesulfonate and polyvinylpyrrolidone.
5. The use of a Mn-doped lithium ferrate according to claim 4, wherein the surfactant is present in an amount of 2 to 10wt% based on the weight of the iron source.
6. The use of the Mn-doped lithium ferrate according to claim 1, wherein the ball milling speed is 200 to 400 r/min; ball milling for 1-3 h;
the feeding speed in the spray drying process is 10-30 ml/min;
the sintering time is 24-48 h.
7. The lithium-supplementing cathode material applied to any one of claims 1 to 6.
8. The use of the lithium-replenishing positive electrode material according to claim 7: the method is characterized in that the method is used for preparing the anode piece of the lithium ion battery.
9. The use of the lithium-replenishing positive electrode material according to claim 8: the lithium ion battery is characterized in that the lithium ion battery is obtained by assembling the positive pole piece, the diaphragm, the negative pole piece and the electrolyte.
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| CN115000362A (en) * | 2022-04-29 | 2022-09-02 | 中南大学 | Li 5 Fe x M y O 4 @ C composite material, preparation thereof and application thereof in lithium ion battery |
| CN115347255A (en) * | 2022-07-12 | 2022-11-15 | 深圳市德方创域新能源科技有限公司 | Positive electrode lithium supplement additive and preparation method and application thereof |
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