CN115566157B - Long cycle life power battery - Google Patents
Long cycle life power battery Download PDFInfo
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Abstract
The invention discloses a long-cycle life power battery, which comprises a positive plate, a negative plate, a diaphragm, electrolyte and a shell, wherein a positive active material in the positive plate is prepared by the following method: 1) Preparing a boron-doped single-arm carbon nanotube; 2) Carrying out hydroxylation modification on the boron-doped single-arm carbon nanotube; 3) Preparing a multi-doped modified single-arm carbon nano tube; 4) Preparing lithium iron phosphate; 5) And coating the lithium iron phosphate material by utilizing the multi-doped modified single-arm carbon nano tube to obtain the anode active material. The long-cycle life power battery provided by the invention has excellent cycle performance, high energy density, good battery multiplying power performance, long service life and good application prospect; according to the invention, the excellent performance of the single-arm carbon nanotube is fully utilized, the single-arm carbon nanotube coated and modified lithium iron phosphate material is prepared by coating and modifying the lithium iron phosphate material, and the single-arm carbon nanotube coated and modified lithium iron phosphate material is used as a positive electrode active material of a battery, so that the electrochemical performance of the battery can be remarkably improved.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a long-cycle-life power battery.
Background
Lithium ion batteries are widely used because of their high energy density, high output power, long cycle life, and low environmental pollution. The lithium iron phosphate is one of the most commonly used positive electrode materials of the current power battery due to the characteristics of high cycle life, good safety, low price and the like, and the optimization of the positive electrode material is an effective method for improving the service performance of the lithium iron phosphate battery.
Electronic conductivity and Li of pure lithium iron phosphate material + The diffusion coefficient is poor, the electrochemical performance is seriously affected, and the further application is limited. At present, ion doping, coating and other technologies are generally adopted to improve the electrochemical performance of the lithium iron phosphate material, so that the performance of a battery prepared from the lithium iron phosphate material is improved. For example, patent CN110233284B discloses a low-temperature type high-energy-density long-cycle lithium iron phosphate battery, which is prepared by doping boron nitride and carbon fiber or carbon nanotube into lithium iron phosphate as a positive electrode material, so that the conductivity of the material can be improved, and the cyclicity and capacity of the battery are greatly improved.
The carbon nano tube has a unique hollow structure, good electric conductivity and mechanical property, and can be applied to the modification of lithium iron phosphate materials; for example, CN101734927a discloses a method for preparing a lithium iron phosphate/carbon nanotube composite material, CN201710326942.2 a lithium iron phosphate/carbon nanotube composite material for a positive electrode material of a lithium battery, a preparation method thereof, CN110233284B and the like. However, carbon nanotubes have a large van der waals force between them due to the entanglement caused by a large aspect ratio and a high energy surface caused by a large specific surface area, and are easily highly aggregated or entangled with each other, so that there is a defect that dispersion is difficult, resulting in difficulty in sufficiently exerting the function of improving electrochemical properties of the carbon nanotubes.
Therefore, there is a need in the art for improvements that provide a more reliable solution.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a device for solving the defects in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme: the long-cycle life power battery comprises a positive plate, a negative plate, a diaphragm, electrolyte and a shell, wherein the positive plate is obtained by coating a mixture consisting of a positive active material, a conductive agent A and a binder A on two sides of an aluminum foil, and the negative plate is obtained by coating a mixture consisting of a negative active material, a conductive agent B and a binder B on two sides of the aluminum foil;
the positive electrode active material is a single-arm carbon nanotube coated modified lithium iron phosphate material, and is prepared by the following method:
1) Preparing a boron-doped single-arm carbon nanotube;
2) Carrying out hydroxylation modification on the boron-doped single-arm carbon nanotube;
3) Preparing a multi-doped modified single-arm carbon nano tube;
4) Preparation of LiFePO 4 ；
5) LiFePO is prepared by utilizing the multi-doping modified single-arm carbon nano tube 4 And coating the material to obtain the positive electrode active material.
Preferably, the negative electrode active material is graphite.
Preferably, the electrolyte in the electrolyte is lithium hexafluorophosphate and/or lithium bisoxalato borate, and the solvent in the electrolyte is one or more of ethylene carbonate, dimethyl glycol, propylene carbonate and vinylene carbonate.
Preferably, the conductive agent A and the conductive agent B are both mixtures of graphene and conductive carbon black, and the mass ratio of the graphene to the conductive carbon black is 1:20-1:8;
the binder A and the binder B are both mixtures of sodium carboxymethyl cellulose and styrene-butadiene rubber aqueous solution, and the solid content of the styrene-butadiene rubber is 35% -58%.
Preferably, the step 1) specifically includes:
adding 25-80 mg of single-arm carbon nanotubes into 10-50 mL of boric acid with the concentration of 0.02-0.1M, performing ultrasonic dispersion for 20-50 min, and then performing freeze drying; transferring the obtained powder into a heating furnace, and in H 2 And (3) heating the mixture with Ar to 850-1100 ℃ at a heating rate of 5-20 ℃/min, preserving heat for 1.5-4 hours, and cooling to obtain the boron-doped single-arm carbon nanotube.
Preferably, the step 2) specifically includes:
adding the boron doped single-arm carbon nanotube and sodium hydroxide solid into acetone, stirring uniformly, ball-milling the obtained mixture for 8-16 h, filtering, sequentially cleaning the obtained solid product to be neutral by ethanol and deionized water, and vacuum drying at 90-120 ℃ for 6-14 h to obtain the hydroxylated boron doped single-arm carbon nanotube.
Preferably, the step 3) specifically includes:
3-1) adding the hydroxylated boron-doped single-arm carbon nanotube obtained in the step 2) into deionized water at 65-85 ℃, and carrying out ultrasonic treatment for 10-30 min to obtain a carbon nanotube dispersion;
3-2) adding the diethyl triamine penta sodium iron acetate into deionized water at 60-85 ℃ and stirring for 5-10 min;
3-3) adding the carbon nanotube dispersion liquid obtained in the step 3-1) into the product obtained in the step 3-2), adding EDCI, stirring at 45-70 ℃ for reaction for 2-5 hours, filtering after the reaction is finished, sequentially cleaning the solid product with deionized water and ethanol, and drying at 50-65 ℃ for 10-28 hours to obtain the multi-doped modified single-arm carbon nanotube.
Preferably, the step 4) specifically includes:
4-1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
4-2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
4-3) mixing solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:1-3;
4-4) placing the precursor solution obtained in the step 1-3) in microwaves, heating at 170-240 ℃ for 20-60 min, cooling after the reaction is finished, filtering, sequentially cleaning a solid product with deionized water and ethanol, vacuum drying at 95-130 ℃ for 4-10 h, cooling, and grinding to obtain LiFePO 4 。
Preferably, the step 5) specifically includes:
5-1) LiFePO obtained in step 4) 4 Mixing with glucose and the multi-doped modified single-arm carbon nano tube obtained in the step 3), adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 1-6 h under the protection of argon at 300-750 r/min, and vacuum drying at 65-90 ℃;
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 600-900 ℃ at 3-15 ℃/min under nitrogen atmosphere, sintering for 8-24 h, cooling, and grinding to obtain the single-arm carbon nanotube coated and modified lithium iron phosphate material, namely the positive electrode active material.
Preferably, the battery is prepared by the steps of:
s1, manufacturing a positive pole piece:
dissolving an anode active material, a conductive agent A and a binder A in deionized water, mixing and homogenizing to obtain anode slurry, coating the anode slurry on two sides of an aluminum foil with the thickness of 5-20 mu m as a current collector, drying, rolling, shearing and slitting to prepare an anode plate;
wherein, the positive electrode active material: conductive agent a: binder a: the mass ratio of deionized water is 82-94: 1.5-8.5:3-14:95-100;
s2, manufacturing a negative pole piece:
dissolving a negative electrode active material, a conductive agent B and a binder B in deionized water, mixing and homogenizing to obtain negative electrode slurry, coating the negative electrode slurry on two sides of an aluminum foil by taking a copper foil with the thickness of 5-20 mu m as a current collector, drying, rolling, shearing and slitting to prepare a negative electrode plate;
Wherein, the negative electrode active material: conductive agent B: binder B: the mass ratio of deionized water is 86-98: 0.5-7:1.5-5.5:95-100;
s3, winding the positive pole piece, the negative pole piece and the diaphragm into a battery core in a winding mode, loading the battery core into a shell, baking the battery core in the shell for 25-60h, and carrying out liquid injection, assembly, formation and capacity division to obtain the long-cycle life power battery.
The beneficial effects of the invention are as follows:
the long-cycle life power battery provided by the invention has excellent cycle performance, high energy density, good battery multiplying power performance, long service life and good application prospect;
in the invention, the excellent performance of the single-arm carbon nano tube is fully utilized, and LiFePO is prepared by using the single-arm carbon nano tube 4 The material is coated and modified to prepare a single-arm carbon nanotube coated and modified lithium iron phosphate material, and the single-arm carbon nanotube coated and modified lithium iron phosphate material is used as an anode active material of a battery, so that the electrochemical performance of the battery can be remarkably improved;
the invention relates to a method for preparing LiFePO by multi-doping modified single-arm carbon nano tube 4 The material is coated, so that the defect that the single-arm carbon nano tube is difficult to disperse is overcome, the function of improving the conductivity can be fully exerted in a lithium iron phosphate positive electrode material system, meanwhile, the enhancement effect of the single-arm carbon nano tube on the conductivity can be further improved through doping B, N and introducing iron ions and sodium ions, and the electrochemical performance of the prepared power battery is obviously improved.
Detailed Description
The present invention is described in further detail below with reference to examples to enable those skilled in the art to practice the same by referring to the description.
It will be understood that terms, such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
The test methods used in the following examples are conventional methods unless otherwise specified. The material reagents and the like used in the following examples are commercially available unless otherwise specified. The following examples were conducted under conventional conditions or conditions recommended by the manufacturer, without specifying the specific conditions. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The invention provides a long-cycle life power battery, which comprises a positive plate, a negative plate, a diaphragm, electrolyte and a shell, wherein the positive plate is obtained by coating a mixture consisting of a positive active material, a conductive agent A and a binder A on two sides of an aluminum foil, and the negative plate is obtained by coating a mixture consisting of a negative active material, a conductive agent B and a binder B on two sides of the aluminum foil;
The positive electrode active material is a single-arm carbon nanotube coated modified lithium iron phosphate material, and is prepared by the following method:
1) Preparing a boron doped single-arm carbon nano tube:
adding 25-80 mg of single-arm carbon nanotubes into 10-50 mL of boric acid with the concentration of 0.02-0.1M, performing ultrasonic dispersion for 20-50 min, and then performing freeze drying; transferring the obtained powder into a heating furnace, and in H 2 And (3) heating the mixture with Ar to 850-1100 ℃ at a heating rate of 5-20 ℃/min, preserving heat for 1.5-4 hours, and cooling to obtain the boron-doped single-arm carbon nanotube.
2) Carrying out hydroxylation modification on the boron doped single-arm carbon nanotube:
adding the boron doped single-arm carbon nanotube and sodium hydroxide solid into acetone, stirring uniformly, ball-milling the obtained mixture for 8-16 h, filtering, sequentially cleaning the obtained solid product to be neutral by ethanol and deionized water, and vacuum drying at 90-120 ℃ for 6-14 h to obtain the hydroxylated boron doped single-arm carbon nanotube.
3) Preparing a multi-doped modified single-arm carbon nano tube:
3-1) adding the hydroxylated boron-doped single-arm carbon nanotube obtained in the step 2) into deionized water at 65-85 ℃, and carrying out ultrasonic treatment for 10-30 min to obtain a carbon nanotube dispersion;
3-2) adding the diethyl triamine penta sodium iron acetate into deionized water at 60-85 ℃ and stirring for 5-10 min;
3-3) adding the carbon nanotube dispersion liquid obtained in the step 3-1) into the product obtained in the step 3-2), adding EDCI, stirring at 45-70 ℃ for reaction for 2-5 hours, filtering after the reaction is finished, sequentially cleaning the solid product with deionized water and ethanol, and drying at 50-65 ℃ for 10-28 hours to obtain the multi-doped modified single-arm carbon nanotube.
4) Preparation of LiFePO 4 ：
4-1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
4-2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
4-3) mixing solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:1-3;
4-4) placing the precursor solution obtained in the step 4-3) in microwaves, heating at 170-240 ℃ for 20-60 min, cooling after the reaction is finished, filtering, sequentially cleaning a solid product with deionized water and ethanol, vacuum drying at 95-130 ℃ for 4-10 h, cooling, and grinding to obtain LiFePO 4 。
5) LiFePO is prepared by utilizing the multi-doping modified single-arm carbon nano tube 4 Coating the materials:
5-1) LiFePO obtained in step 4) 4 Mixing with glucose and the multi-doped modified single-arm carbon nano tube obtained in the step 3), adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 1-6 h under the protection of argon at 300-750 r/min, and vacuum drying at 65-90 ℃;
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 600-900 ℃ at 3-15 ℃/min under nitrogen atmosphere, sintering for 8-24 h, cooling, and grinding to obtain the single-arm carbon nanotube coated and modified lithium iron phosphate material, namely the positive electrode active material.
In a preferred embodiment, the anode active material is graphite, and the diaphragm adopts a PP/PE/PP three-layer composite diaphragm
In a preferred embodiment, the electrolyte in the electrolyte is lithium hexafluorophosphate and/or lithium bisoxalato borate, and the solvent in the electrolyte is one or more of ethylene carbonate, dimethyl glycol, propylene carbonate and vinylene carbonate.
In a preferred embodiment, the conductive agent A and the conductive agent B are both mixtures of graphene and conductive carbon black, and the mass ratio of the graphene to the conductive carbon black is 1:20-1:8;
the binder A and the binder B are both mixtures of sodium carboxymethyl cellulose and styrene-butadiene rubber aqueous solution, and the solid content of the styrene-butadiene rubber is 35% -58%.
In a preferred embodiment, the long cycle life power cell is prepared by the steps of:
s1, manufacturing a positive pole piece:
dissolving an anode active material, a conductive agent A and a binder A in deionized water, mixing and homogenizing to obtain anode slurry, coating the anode slurry on two sides of an aluminum foil with the thickness of 5-20 mu m as a current collector, drying, rolling, shearing and slitting to prepare an anode plate;
Wherein, the positive electrode active material: conductive agent a: binder a: the mass ratio of deionized water is 82-94: 1.5-8.5:3-14:95-100;
s2, manufacturing a negative pole piece:
dissolving a negative electrode active material, a conductive agent B and a binder B in deionized water, mixing and homogenizing to obtain negative electrode slurry, coating the negative electrode slurry on two sides of an aluminum foil by taking a copper foil with the thickness of 5-20 mu m as a current collector, drying, rolling, shearing and slitting to prepare a negative electrode plate;
wherein, the negative electrode active material: conductive agent B: binder B: the mass ratio of deionized water is 86-98: 0.5-7:1.5-5.5:95-100;
s3, winding the positive pole piece, the negative pole piece and the diaphragm into a battery core in a winding mode, loading the battery core into a shell, baking the battery core in the shell for 25-60h, and carrying out liquid injection, assembly, formation and capacity division to obtain the long-cycle life power battery.
In the invention, the excellent performance of the single-arm carbon nano tube is fully utilized, and LiFePO is prepared by using the single-arm carbon nano tube 4 The lithium iron phosphate material with the single-arm carbon nano tube coated and modified is prepared by coating and modifying the material, and can be used as a positive electrode active material of a battery, so that the electrochemical performance of the battery can be obviously improved, and the battery provided by the invention has excellent cycle performance, high energy density and high rate performance. The following mainly describes the main principle of the positive electrode active material of the present invention to facilitate understanding of the present invention.
The single-arm carbon nano tube has high length-diameter ratio and high flexibility, and the single-arm carbon nano tube is adopted to coat the positive electrode active material, so that positive electrode material particles can be connected together, the connection strength among the particles is improved, and the positive electrode adhesive force is improved, thereby constructing a three-dimensional conductive network in the positive electrode active material, remarkably improving the conductive performance, the energy density, the adhesive force and the safety, and improving the cycle performance of a battery. And the single-arm carbon nanotube exhibits enhanced performance comparable to that of the multi-arm carbon nanotube with a smaller addition amount than the multi-arm carbon nanotube.
Although the single-arm carbon nanotube has the advantages, the defects of easy agglomeration and difficult dispersion caused by large surface energy greatly limit the application of the single-arm carbon nanotube as a modifying reagent of a positive electrode material, and the reinforcing effect of the single-arm carbon nanotube on the positive electrode material system is difficult to fully exert due to the agglomeration. In the present invention, the defect can be overcome by modifying the single-arm carbon nanotube, and the following description will be made.
Firstly, in the invention, the boron doped single-arm carbon nanotube is prepared by doping B in the carbon nanotube, so that the charge transfer amount between the carbon nanotube and Li in the nitrogen doped carbon modified lithium iron phosphate anode material can be improved, and the conductivity between the carbon nanotube and Li is improved ([ 1] generation sharp peak. Theoretical research on the influence of doping on the conductivity of the carbon nanotube [ D ]. North China university of science, 2017). The doping of B can reduce the energy barrier of lithium penetrating through the wall of the carbon nano tube, and meanwhile, the doping of B can reduce the generation energy of the same topological defects, so that more topological defects appear and the diffusion of lithium ions is facilitated.
The invention further carries out hydroxylation on the boron doped single-arm carbon nanotube, and then adopts diethylenetriamine pentaacetic acid iron sodium to carry out multi-doping modification on the single-arm carbon nanotube. The chemical structural formula of the diethyl triamine penta sodium iron acetate is shown as the following formula I:
it can be seen that the sodium iron diethylenetriamine pentaacetate has a rich carboxyl function, on which iron ions and sodium ions are complexed, and which contains N element.
According to the invention, the diethyl triamine sodium iron pentaacetate is uniformly and firmly grafted to the surface of the boron-doped single-arm carbon nanotube through the condensation reaction of the carboxyl functional group on the diethyl triamine sodium iron pentaacetate and the hydroxyl functional group of the boron-doped single-arm carbon nanotube, so that on one hand, the N doping of the boron-doped single-arm carbon nanotube is realized, and on the other hand, a large amount of iron ions and sodium ions which can be uniformly loaded can be simultaneously introduced to the surface of the boron-doped single-arm carbon nanotube.
On one hand, N and C are combined to form a C-N bond, and meanwhile, an N atom loses one electron, so that the electron concentration of the single-arm carbon nanotube is increased, and the conductivity of the single-arm carbon nanotube can be improved ([ 1] Zhang Yadong. Experimental study [ D ] of improving the conductivity of the carbon nanotube by transition metal doping is performed; on the other hand, the doping of N can also obviously promote the hydrophilicity of the single-arm carbon nano tube, improve the dispersibility of the single-arm carbon nano tube and overcome the defect that the conventional single-arm carbon nano tube is easy to agglomerate.
The single-arm carbon nanotube is doped with iron ions, so that the Fermi level can be reduced, the energy band structure of the single-arm carbon nanotube is changed, the contact potential barrier between the single-arm carbon nanotube and an electrode is reduced, and the conductivity of the single-arm carbon nanotube is improved; furthermore, the iron ions in the invention can be uniformly loaded on the surface of the three-dimensional network structure of the single-arm carbon nano tube, so that the state density near the fermi level can be increased, a stable conductive network is constructed, and the conductivity is improved.
The single-arm carbon nanotube is doped with sodium ions, so that the surface active reaction sites of the single-arm carbon nanotube can be increased, a stable conductive network can be constructed in the battery active material, and the conductivity of the single-arm carbon nanotube can be further improved.
The introduction of iron ions and sodium ions can enhance the surface contact between the single-arm carbon nanotube and the battery active material, and can improve the dispersibility of the single-arm carbon nanotube in an electric positive electrode material system.
In the invention, liFePO is prepared by multi-doping modified single-arm carbon nano tube 4 The material is coated, a three-dimensional space conductive network can be formed, and the electron conduction capacity and the cycling stability of the lithium iron phosphate anode material are enhanced; and simultaneously when the carbon nano tube is coated in situ, the carbonization of glucose can form a CB (carbon black) coating layer to coat LiFePO 4 Particle surface can inhibit particle agglomeration or enlargement, and enhance particle conductivity; the invention leads LiFePO to be realized by the combined action of the multi-doping modified single-arm carbon nano tube and CB 4 The material has better conductivity and can improve the multiplying power and the cycle performance of lithium iron phosphate.
The invention relates to a method for preparing LiFePO by multi-doping modified single-arm carbon nano tube 4 The material is coated, so that the defect that the single-arm carbon nano tube is difficult to disperse is overcome, the function of improving the conductivity and the mechanical property can be fully exerted in a lithium iron phosphate positive electrode material system, and meanwhile, the enhancement effect of the single-arm carbon nano tube on the conductivity can be further improved by doping B, N and introducing iron ions and sodium ions.
The foregoing is a general inventive concept and the following detailed examples and comparative examples are provided on the basis thereof to further illustrate the invention.
Example 1
The long-cycle life power battery comprises a positive plate, a negative plate, a diaphragm, electrolyte and a shell, wherein the positive plate is obtained by coating a mixture consisting of a positive active material, a conductive agent A and a binder A on two sides of an aluminum foil, and the negative plate is obtained by coating a mixture consisting of a negative active material, a conductive agent B and a binder B on two sides of the aluminum foil;
The long-cycle life power battery is prepared by the following steps:
s1, manufacturing a positive pole piece:
dissolving an anode active material, a conductive agent A and a binder A in deionized water, mixing and homogenizing to obtain anode slurry, coating the anode slurry on two sides of an aluminum foil with the thickness of 15 mu m as a current collector, drying, rolling, shearing and slitting to prepare an anode plate; wherein, the positive electrode active material: conductive agent a: binder a: the mass ratio of deionized water is 92:6.5:7:100;
s2, manufacturing a negative pole piece:
dissolving a negative electrode active material, a conductive agent B and a binder B in deionized water, mixing and homogenizing to obtain a negative electrode slurry, coating the negative electrode slurry on two sides of an aluminum foil by using a copper foil with the diameter of 18 mu m as a current collector, drying, rolling, shearing and slitting to prepare a negative electrode plate;
wherein, the negative electrode active material: conductive agent B: binder B: the mass ratio of deionized water is 95:2.4:4.3:100;
s3, winding the positive pole piece, the negative pole piece and the diaphragm into a battery core in a winding mode, loading the battery core into a shell, baking for 30 hours under the vacuum condition of the shell, and carrying out liquid injection, assembly, formation and capacity division at the baking temperature of 85 ℃ to obtain the long-cycle life power battery. Wherein the assembly is protected by argon.
The negative electrode active material is graphite, and the diaphragm adopts a PP/PE/PP three-layer composite diaphragm with the thickness of 20 um. The electrolyte in the electrolyte is 1mol/L lithium hexafluorophosphate, and the solvent in the electrolyte is a mixture of ethylene carbonate, dimethyl carbonate and dimethyl glycol. The conductive agent A and the conductive agent B are both mixtures of graphene and conductive carbon black, and the mass ratio of the graphene to the conductive carbon black is 1:15; the binder A and the binder B are both mixtures of sodium carboxymethyl cellulose and styrene-butadiene rubber aqueous solution, and the solid content of the styrene-butadiene rubber is 42%.
In this embodiment, the positive electrode active material is a single-arm carbon nanotube coated modified lithium iron phosphate material, and is prepared by the following method:
1) Preparing a boron doped single-arm carbon nano tube:
adding 60mg of single-arm carbon nano tube into 30mL of boric acid with the concentration of 0.04M, performing ultrasonic dispersion for 30min, and then performing freeze drying; transferring the obtained powder into a heating furnace, and in H 2 And (3) heating the mixture with Ar to 980 ℃ at a heating rate of 10 ℃/min, preserving heat for 3 hours, and cooling to obtain the boron-doped single-arm carbon nanotube.
2) Carrying out hydroxylation modification on the boron doped single-arm carbon nanotube:
Adding 0.1g of boron doped single-arm carbon nanotube and 3g of sodium hydroxide solid into acetone, stirring uniformly, ball-milling the obtained mixture for 10 hours, filtering, sequentially cleaning the obtained solid product to be neutral by ethanol and deionized water, and vacuum drying at 110 ℃ for 10 hours to obtain the hydroxylated boron doped single-arm carbon nanotube.
3) Preparing a multi-doped modified single-arm carbon nano tube:
3-1) adding the hydroxylated boron-doped single-arm carbon nanotube obtained in the step 2) into deionized water at 70 ℃, and carrying out ultrasonic treatment for 15min to obtain a carbon nanotube dispersion liquid;
3-2) adding the diethyl triamine penta sodium iron acetate into deionized water at 65 ℃ and stirring for 7min;
3-3) adding the carbon nanotube dispersion liquid obtained in the step 3-1) into the product obtained in the step 3-2), adding EDCI (1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride), stirring at 55 ℃ for reaction for 4 hours, filtering after the reaction is finished, sequentially cleaning a solid product with deionized water and ethanol, and drying at 60 ℃ for 18 hours to obtain the multi-doped modified single-arm carbon nanotube.
4) Preparation of LiFePO 4 ：
4-1) FeSO is carried out 4 ·7H 2 O adding deionized water containing ethanolAdding ascorbic acid, stirring and dissolving to obtain solution A;
4-2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
4-3) mixing solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:2;
4-4) placing the precursor solution obtained in the step 4-3) in microwaves, heating at 220 ℃ for 35min, cooling after the reaction is finished, filtering, sequentially cleaning a solid product with deionized water and ethanol, vacuum drying at 115 ℃ for 6h, cooling, and grinding to obtain LiFePO 4 。
5) LiFePO is prepared by utilizing the multi-doping modified single-arm carbon nano tube 4 Coating the materials:
5-1) LiFePO obtained in step 4) 4 Mixing with glucose and the multi-doped modified single-arm carbon nano tube obtained in the step 3), adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 4 hours under the protection of argon gas and at 450r/min, and vacuum drying at 80 ℃; wherein, liFePO 4 : glucose: the mass ratio of the multi-doped modified single-arm carbon nano tube is 100:12:0.2.
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 830 ℃ at 10 ℃/min under nitrogen atmosphere, sintering for 12 hours, cooling, and grinding to obtain the single-arm carbon nanotube coated modified lithium iron phosphate material, namely the positive electrode active material.
Example 2
The long-cycle life power battery comprises a positive plate, a negative plate, a diaphragm, electrolyte and a shell, wherein the positive plate is obtained by coating a mixture consisting of a positive active material, a conductive agent A and a binder A on two sides of an aluminum foil, and the negative plate is obtained by coating a mixture consisting of a negative active material, a conductive agent B and a binder B on two sides of the aluminum foil;
the long-cycle life power battery is prepared by the following steps:
s1, manufacturing a positive pole piece:
dissolving an anode active material, a conductive agent A and a binder A in deionized water, mixing and homogenizing to obtain anode slurry, coating the anode slurry on two sides of an aluminum foil with the thickness of 15 mu m as a current collector, drying, rolling, shearing and slitting to prepare an anode plate; wherein, the positive electrode active material: conductive agent a: binder a: the mass ratio of deionized water is 92:6.5:7:100;
s2, manufacturing a negative pole piece:
dissolving a negative electrode active material, a conductive agent B and a binder B in deionized water, mixing and homogenizing to obtain a negative electrode slurry, coating the negative electrode slurry on two sides of an aluminum foil by using a copper foil with the diameter of 18 mu m as a current collector, drying, rolling, shearing and slitting to prepare a negative electrode plate;
Wherein, the negative electrode active material: conductive agent B: binder B: the mass ratio of deionized water is 95:2.4:4.3:100;
s3, winding the positive pole piece, the negative pole piece and the diaphragm into a battery core in a winding mode, loading the battery core into a shell, baking for 30 hours under the vacuum condition of the shell, and carrying out liquid injection, assembly, formation and capacity division at the baking temperature of 85 ℃ to obtain the long-cycle life power battery. Wherein the assembly is protected by argon.
The negative electrode active material is graphite, and the diaphragm adopts a PP/PE/PP three-layer composite diaphragm with the thickness of 20 um. The electrolyte in the electrolyte is 1mol/L lithium hexafluorophosphate, and the solvent in the electrolyte is a mixture of ethylene carbonate, dimethyl carbonate and dimethyl glycol. The conductive agent A and the conductive agent B are both mixtures of graphene and conductive carbon black, and the mass ratio of the graphene to the conductive carbon black is 1:15; the binder A and the binder B are both mixtures of sodium carboxymethyl cellulose and styrene-butadiene rubber aqueous solution, and the solid content of the styrene-butadiene rubber is 42%.
In this embodiment, the positive electrode active material is a single-arm carbon nanotube coated modified lithium iron phosphate material, and is prepared by the following method:
1) Preparing a boron doped single-arm carbon nano tube:
60mg of single-arm carbon nanotube is added to 30mL of the solution with the concentration of 0.04MDispersing in boric acid by ultrasonic for 30min, and freeze-drying; transferring the obtained powder into a heating furnace, and in H 2 And (3) heating the mixture with Ar to 980 ℃ at a heating rate of 10 ℃/min, preserving heat for 3 hours, and cooling to obtain the boron-doped single-arm carbon nanotube.
2) Carrying out hydroxylation modification on the boron doped single-arm carbon nanotube:
adding 0.1g of boron doped single-arm carbon nanotube and 3g of sodium hydroxide solid into acetone, stirring uniformly, ball-milling the obtained mixture for 10 hours, filtering, sequentially cleaning the obtained solid product to be neutral by ethanol and deionized water, and vacuum drying at 110 ℃ for 10 hours to obtain the hydroxylated boron doped single-arm carbon nanotube.
3) Preparing a multi-doped modified single-arm carbon nano tube:
3-1) adding the hydroxylated boron-doped single-arm carbon nanotube obtained in the step 2) into deionized water at 70 ℃, and carrying out ultrasonic treatment for 15min to obtain a carbon nanotube dispersion liquid;
3-2) adding the diethyl triamine penta sodium iron acetate into deionized water at 65 ℃ and stirring for 7min;
3-3) adding the carbon nanotube dispersion liquid obtained in the step 3-1) into the product obtained in the step 3-2), adding EDCI (1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride), stirring at 55 ℃ for reaction for 4 hours, filtering after the reaction is finished, sequentially cleaning a solid product with deionized water and ethanol, and drying at 60 ℃ for 18 hours to obtain the multi-doped modified single-arm carbon nanotube.
4) Preparation of LiFePO 4 ：
4-1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
4-2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
4-3) mixing solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:2;
4-4) subjecting the precursor obtained in step 4-3)Heating the solution in microwave at 220deg.C for 35min, cooling after reaction, filtering, sequentially cleaning the solid product with deionized water and ethanol, vacuum drying at 115deg.C for 6 hr, cooling, and pulverizing to obtain LiFePO 4 。
5) LiFePO is prepared by utilizing the multi-doping modified single-arm carbon nano tube 4 Coating the materials:
5-1) LiFePO obtained in step 4) 4 Mixing with glucose and the multi-doped modified single-arm carbon nano tube obtained in the step 3), adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 4 hours under the protection of argon gas and at 450r/min, and vacuum drying at 80 ℃; wherein, liFePO 4 : glucose: the mass ratio of the multi-doped modified single-arm carbon nano tube is 100:12:0.4.
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 830 ℃ at 10 ℃/min under nitrogen atmosphere, sintering for 12 hours, cooling, and grinding to obtain the single-arm carbon nanotube coated modified lithium iron phosphate material, namely the positive electrode active material.
Example 3
The long-cycle life power battery comprises a positive plate, a negative plate, a diaphragm, electrolyte and a shell, wherein the positive plate is obtained by coating a mixture consisting of a positive active material, a conductive agent A and a binder A on two sides of an aluminum foil, and the negative plate is obtained by coating a mixture consisting of a negative active material, a conductive agent B and a binder B on two sides of the aluminum foil;
the long-cycle life power battery is prepared by the following steps:
s1, manufacturing a positive pole piece:
dissolving an anode active material, a conductive agent A and a binder A in deionized water, mixing and homogenizing to obtain anode slurry, coating the anode slurry on two sides of an aluminum foil with the thickness of 15 mu m as a current collector, drying, rolling, shearing and slitting to prepare an anode plate; wherein, the positive electrode active material: conductive agent a: binder a: the mass ratio of deionized water is 92:6.5:7:100;
s2, manufacturing a negative pole piece:
dissolving a negative electrode active material, a conductive agent B and a binder B in deionized water, mixing and homogenizing to obtain a negative electrode slurry, coating the negative electrode slurry on two sides of an aluminum foil by using a copper foil with the diameter of 18 mu m as a current collector, drying, rolling, shearing and slitting to prepare a negative electrode plate;
Wherein, the negative electrode active material: conductive agent B: binder B: the mass ratio of deionized water is 95:2.4:4.3:100;
s3, winding the positive pole piece, the negative pole piece and the diaphragm into a battery core in a winding mode, loading the battery core into a shell, baking for 30 hours under the vacuum condition of the shell, and carrying out liquid injection, assembly, formation and capacity division at the baking temperature of 85 ℃ to obtain the long-cycle life power battery. Wherein the assembly is protected by argon.
The negative electrode active material is graphite, and the diaphragm adopts a PP/PE/PP three-layer composite diaphragm with the thickness of 20 um. The electrolyte in the electrolyte is 1mol/L lithium hexafluorophosphate, and the solvent in the electrolyte is a mixture of ethylene carbonate, dimethyl carbonate and dimethyl glycol. The conductive agent A and the conductive agent B are both mixtures of graphene and conductive carbon black, and the mass ratio of the graphene to the conductive carbon black is 1:15; the binder A and the binder B are both mixtures of sodium carboxymethyl cellulose and styrene-butadiene rubber aqueous solution, and the solid content of the styrene-butadiene rubber is 42%.
In this embodiment, the positive electrode active material is a single-arm carbon nanotube coated modified lithium iron phosphate material, and is prepared by the following method:
1) Preparing a boron doped single-arm carbon nano tube:
adding 60mg of single-arm carbon nano tube into 30mL of boric acid with the concentration of 0.04M, performing ultrasonic dispersion for 30min, and then performing freeze drying; transferring the obtained powder into a heating furnace, and in H 2 And (3) heating the mixture with Ar to 980 ℃ at a heating rate of 10 ℃/min, preserving heat for 3 hours, and cooling to obtain the boron-doped single-arm carbon nanotube.
2) Carrying out hydroxylation modification on the boron doped single-arm carbon nanotube:
adding 0.1g of boron doped single-arm carbon nanotube and 3g of sodium hydroxide solid into acetone, stirring uniformly, ball-milling the obtained mixture for 10 hours, filtering, sequentially cleaning the obtained solid product to be neutral by ethanol and deionized water, and vacuum drying at 110 ℃ for 10 hours to obtain the hydroxylated boron doped single-arm carbon nanotube.
3) Preparing a multi-doped modified single-arm carbon nano tube:
3-1) adding the hydroxylated boron-doped single-arm carbon nanotube obtained in the step 2) into deionized water at 70 ℃, and carrying out ultrasonic treatment for 15min to obtain a carbon nanotube dispersion liquid;
3-2) adding the diethyl triamine penta sodium iron acetate into deionized water at 65 ℃ and stirring for 7min;
3-3) adding the carbon nanotube dispersion liquid obtained in the step 3-1) into the product obtained in the step 3-2), adding EDCI (1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride), stirring at 55 ℃ for reaction for 4 hours, filtering after the reaction is finished, sequentially cleaning a solid product with deionized water and ethanol, and drying at 60 ℃ for 18 hours to obtain the multi-doped modified single-arm carbon nanotube.
4) Preparation of LiFePO 4 ：
4-1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
4-2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
4-3) mixing solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:2;
4-4) placing the precursor solution obtained in the step 4-3) in microwaves, heating at 220 ℃ for 35min, cooling after the reaction is finished, filtering, sequentially cleaning a solid product with deionized water and ethanol, vacuum drying at 115 ℃ for 6h, cooling, and grinding to obtain LiFePO 4 。
5) LiFePO is prepared by utilizing the multi-doping modified single-arm carbon nano tube 4 Coating the materials:
5-1) LiFePO obtained in step 4) 4 Mixing with glucose and the multi-doped modified single-arm carbon nano tube obtained in the step 3),adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 4 hours under the protection of argon gas at 450r/min, and vacuum drying at 80 ℃; wherein, liFePO 4 : glucose: the mass ratio of the multi-doped modified single-arm carbon nano tube is 100:12:0.6.
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 830 ℃ at 10 ℃/min under nitrogen atmosphere, sintering for 12 hours, cooling, and grinding to obtain the single-arm carbon nanotube coated modified lithium iron phosphate material, namely the positive electrode active material.
Comparative example 1
This example is substantially the same as example 2, except that: the positive electrode active material in this example is a lithium iron phosphate material, which is prepared by the following method:
1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
3) Solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:2;
4) And 3) placing the precursor liquid obtained in the step 3) in microwaves, heating for 35min at 220 ℃, cooling after the reaction is finished, filtering, sequentially cleaning a solid product by deionized water and ethanol, vacuum drying for 6h at 115 ℃, cooling, and grinding to obtain the lithium iron phosphate material.
Comparative example 2
This example is substantially the same as example 2, except that: the positive electrode active material in this example was prepared by the following method:
1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
3) Solution A,Solutions B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:2;
4) Placing the precursor liquid obtained in the step 3) into microwaves, heating at 220 ℃ for 35min, cooling after the reaction is finished, filtering, sequentially cleaning a solid product with deionized water and ethanol, vacuum drying at 115 ℃ for 6h, cooling, and grinding to obtain LiFePO 4 。
5) LiFePO using single arm carbon nano tube 4 Coating the materials:
LiFePO obtained in step 4) 4 Mixing with glucose and single-arm carbon nanotubes, adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 4 hours under the protection of argon gas and at 450r/min, and vacuum drying at 80 ℃; wherein, liFePO 4 : glucose: the mass ratio of the single-arm carbon nanotubes is 100:12:0.4.
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 830 ℃ at 10 ℃/min under nitrogen atmosphere, sintering for 12 hours, cooling, and grinding to obtain the positive electrode active material.
Comparative example 3
This example is substantially the same as example 2, except that: the positive electrode active material in this example was prepared by the following method:
1) Preparing a boron doped single-arm carbon nano tube:
adding 60mg of single-arm carbon nano tube into 30mL of boric acid with the concentration of 0.04M, performing ultrasonic dispersion for 30min, and then performing freeze drying; transferring the obtained powder into a heating furnace, and in H 2 And (3) heating the mixture with Ar to 980 ℃ at a heating rate of 10 ℃/min, preserving heat for 3 hours, and cooling to obtain the boron-doped single-arm carbon nanotube.
2) Preparation of LiFePO 4 ：
2-1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
2-2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
2-3) mixing solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:2;
2-4) placing the precursor solution obtained in the step 2-3) in microwaves, heating at 220 ℃ for 35min, cooling after the reaction is finished, filtering, sequentially cleaning a solid product with deionized water and ethanol, vacuum drying at 115 ℃ for 6h, cooling, and grinding to obtain LiFePO 4 。
3) LiFePO is prepared by utilizing the multi-doping modified single-arm carbon nano tube 4 Coating the materials:
3-1) LiFePO obtained in step 4) 4 Mixing with glucose and the boron-doped single-arm carbon nanotube obtained in the step 1), adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 4 hours under the protection of argon gas and at 450r/min, and vacuum drying at 80 ℃; wherein, liFePO 4 : glucose: the mass ratio of the boron doped single-arm carbon nano tube is 100:12:0.4.
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 830 ℃ at 10 ℃/min under nitrogen atmosphere, sintering for 12 hours, cooling, and grinding to obtain the positive electrode active material.
The single-arm carbon nanotubes used in the above examples and comparative examples were the same, and were 1-2nm in diameter and 20 μm in length, and were purchased from Shanghai Michlin Biochemical technologies Co., ltd.
The following performance tests were conducted on the batteries produced in examples 1 to 3 and comparative examples 1 to 3:
and (3) testing the circularity: charging to 3.6V at 3C, standing, discharging to 2.5V at 3C, and recording as a charge-discharge cycle, the test results are shown in Table 1 below
TABLE 1
| 3C discharge capacity (mA h) | Capacity retention after 1000 weeks of cycling at 45 DEG C | Capacity retention after 2000 weeks of cycling at 45 ℃C | |
| Example 1 | 2358 | 91.5% | 86.3% |
| Example 2 | 2362 | 90.8% | 86.5% |
| Example 3 | 2366 | 91.1% | 87.2% |
| Comparative example 1 | 1625 | 68.2% | 63.9% |
| Comparative example 2 | 1894 | 73.4% | 68.7% |
| Comparative example 3 | 2023 | 77.9% | 72.3% |
As can be seen from the test results of table 1, the batteries prepared in examples 1 to 3 of the present invention still have a capacity retention rate of 86% or more after 2000 cycles of 3C, and have excellent cycle performance; in comparative examples 1 to 3, the cycle performance was greatly reduced because the positive electrode material was not coated with the single-arm carbon nanotube-modified lithium iron phosphate material of the present invention.
Although embodiments of the present invention have been disclosed above, it is not limited to the use of the description and embodiments, it is well suited to various fields of use for the invention, and further modifications may be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the particular details without departing from the general concepts defined in the claims and the equivalents thereof.
Claims (7)
1. The utility model provides a long cycle life power battery, includes positive plate, negative plate, diaphragm, electrolyte and shell, the positive plate obtains through coating the mixture that positive electrode active material, conductive agent A and binder A constitute on aluminium foil two sides, the negative plate obtains through coating the mixture that negative electrode active material, conductive agent B and binder B constitute on aluminium foil two sides, its characterized in that:
the positive electrode active material is a single-walled carbon nanotube coated modified lithium iron phosphate material, and is prepared by the following method:
1) Preparing a boron doped single-walled carbon nanotube;
2) Carrying out hydroxylation modification on the boron doped single-walled carbon nanotube;
3) Preparing a multi-doped modified single-walled carbon nanotube;
4) Preparation of LiFePO 4 ；
5) LiFePO using the multi-doped modified single-walled carbon nanotube 4 Coating the material to obtain the positive electrode active material;
the step 1) specifically comprises the following steps:
25-80 mg single-wall carbon nanoAdding the rice tube into 10-50 mL boric acid with the concentration of 0.02-0.1M, performing ultrasonic dispersion for 20-50 min, and then performing freeze drying; transferring the obtained powder into a heating furnace, and in H 2 Raising the temperature to 850-1100 ℃ at a heating rate of 5-20 ℃/min under the condition of mixed gas with Ar, preserving heat for 1.5-4 h, and cooling to obtain the boron doped single-walled carbon nanotube;
the step 2) specifically comprises the following steps:
adding boron doped single-walled carbon nanotubes and sodium hydroxide solid into acetone, stirring uniformly, ball-milling the obtained mixture for 8-16 h, filtering, sequentially cleaning the obtained solid product to be neutral by ethanol and deionized water, and vacuum-drying at 90-120 ℃ for 6-14 h to obtain hydroxylated boron doped single-walled carbon nanotubes;
the step 3) is specifically as follows:
3-1) adding the hydroxylated boron doped single-walled carbon nanotube obtained in the step 2) into deionized water at 65-85 ℃, and carrying out ultrasonic treatment for 10-30 min to obtain a carbon nanotube dispersion;
3-2) adding the diethyl triamine penta sodium iron acetate into deionized water at 60-85 ℃ and stirring for 5-10 min;
3-3) adding the carbon nano tube dispersion liquid obtained in the step 3-1) into the product obtained in the step 3-2), adding EDCI, stirring at 45-70 ℃ for reaction for 2-5 hours, filtering after the reaction is finished, sequentially cleaning the solid product with deionized water and ethanol, and drying at 50-65 ℃ for 10-28 hours to obtain the multi-doped modified single-walled carbon nano tube.
2. The long cycle life power cell of claim 1, wherein said negative electrode active material is graphite.
3. The long-life power cell of claim 1, wherein the electrolyte in the electrolyte is lithium hexafluorophosphate and/or lithium bis (oxalato) borate, and the solvent in the electrolyte is one or more of ethylene carbonate, dimethyl glycol, propylene carbonate, and vinylene carbonate.
4. The long-cycle life power cell of claim 1, wherein the conductive agent a and the conductive agent B are both a mixture of graphene and conductive carbon black, and the mass ratio of graphene to conductive carbon black is 1:20-1:8;
the binder A and the binder B are both mixtures of sodium carboxymethyl cellulose and styrene-butadiene rubber aqueous solution, and the solid content of the styrene-butadiene rubber is 35% -58%.
5. The long cycle life power cell of claim 1, wherein said step 4) is specifically:
4-1) FeSO is carried out 4 ·7H 2 Adding O into deionized water containing ethanol, adding ascorbic acid, and stirring for dissolving to obtain solution A;
4-2) LiOH.H 2 Adding O into deionized water, stirring and dissolving to obtain solution B;
4-3) mixing solution A, solution B and H 3 PO 4 Mixing and stirring the solutions, and regulating the pH of the reaction system to 5-6 to obtain a precursor solution; wherein, according to Fe: p: adding raw materials in a molar ratio of Li of 1:1:1-3;
4-4) placing the precursor solution obtained in the step 4-3) into microwaves, heating for 20-60 min at 170-240 ℃, cooling after the reaction is finished, filtering, sequentially cleaning a solid product by deionized water and ethanol, vacuum drying for 4-10 h at 95-130 ℃, cooling, and grinding to obtain LiFePO 4 。
6. The long cycle life power cell of claim 5, wherein said step 5) is specifically:
5-1) LiFePO obtained in step 4) 4 Mixing with glucose and the multi-doped modified single-walled carbon nanotube obtained in the step 3), adding the obtained mixture into a ball mill, taking acetone as a ball milling medium, ball milling for 1-6 h under the protection of argon gas at 300-750 r/min, and vacuum drying at 65-90 ℃;
5-2) placing the product obtained in the step 5-1) in a tube furnace, heating to 600-900 ℃ at 3-15 ℃/min under nitrogen atmosphere, sintering for 8-24 h, cooling, and grinding to obtain the single-walled carbon nanotube coated modified lithium iron phosphate material, namely the positive electrode active material.
7. The long cycle life power cell of claim 6, wherein the cell is prepared by:
S1, manufacturing a positive pole piece:
dissolving an anode active material, a conductive agent A and a binder A in deionized water, mixing and homogenizing to obtain anode slurry, coating the anode slurry on two sides of an aluminum foil with the thickness of 5-20 mu m as a current collector, drying, rolling, shearing and slitting to prepare an anode plate;
wherein, the positive electrode active material: conductive agent a: binder a: the mass ratio of deionized water is 82-94: 1.5-8.5:3-14:95-100;
s2, manufacturing a negative pole piece:
dissolving a negative electrode active material, a conductive agent B and a binder B in deionized water, mixing and homogenizing to obtain negative electrode slurry, coating the negative electrode slurry on two sides of an aluminum foil by using a copper foil with the thickness of 5-20 mu m as a current collector, drying, rolling, shearing and slitting to prepare a negative electrode plate;
wherein, the negative electrode active material: conductive agent B: binder B: the mass ratio of the deionized water is 86-98: 0.5-7:1.5-5.5:95-100;
s3, winding the positive pole piece, the negative pole piece and the diaphragm into a battery core in a winding mode, loading the battery core into a shell, baking the battery core in the shell for 25-60h, and carrying out liquid injection, assembly, formation and capacity division to obtain the long-cycle life power battery.
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| CN110364761A (en) * | 2019-07-17 | 2019-10-22 | 江西省汇亿新能源有限公司 | A high energy density long cycle lithium iron phosphate battery |
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