阅读说明：本技术 磷酸铁锂电池的水系正极浆料及其制备方法 (Water-based positive electrode slurry of lithium iron phosphate battery and preparation method thereof ) 是由 不公告发明人 于 2019-09-04 设计创作，主要内容包括：本发明公开了一种磷酸铁锂电池的水系正极浆料及其制备方法,水系正极浆料包括原料及其重量份数如下：磷酸铁锂90-93份、复合石墨烯导电浆料2-3份、水性粘结剂3-5份、导电剂1-2份,还包括去离子水；所述水系正极浆料的粘度为3000mPa·s-6000mPa·s。本发明的磷酸铁锂电池的水系正极浆料,以去离子水作为分散介质,改善水系正极浆料的分散性,避免了使用有机溶剂造成的环境污染,更加环保及安全；在水系正极浆料的组分中,优化了导电剂和水性粘结剂的含量,同时还使用水系石墨烯复合导电浆为导电剂,能够降低电池欧姆内阻和极化内阻,提高锂电池的高功率启动性能。(The invention discloses a water-based positive electrode slurry of a lithium iron phosphate battery and a preparation method thereof, wherein the water-based positive electrode slurry comprises the following raw materials in parts by weight: 90-93 parts of lithium iron phosphate, 2-3 parts of composite graphene conductive slurry, 3-5 parts of a water-based binder, 1-2 parts of a conductive agent and deionized water; the viscosity of the aqueous positive electrode slurry is 3000mPa & s-6000mPa & s. According to the water-based positive electrode slurry of the lithium iron phosphate battery, deionized water is used as a dispersion medium, so that the dispersibility of the water-based positive electrode slurry is improved, the environmental pollution caused by the use of an organic solvent is avoided, and the water-based positive electrode slurry is more environment-friendly and safer; in the components of the aqueous positive electrode slurry, the contents of a conductive agent and an aqueous binder are optimized, and meanwhile, the aqueous graphene composite conductive slurry is used as the conductive agent, so that the ohmic internal resistance and the polarization internal resistance of the battery can be reduced, and the high-power starting performance of the lithium battery is improved.)

1. The water-based positive electrode slurry of the lithium iron phosphate battery is characterized by comprising the following raw materials in parts by weight: 90-93 parts of lithium iron phosphate, 2-3 parts of composite graphene conductive slurry, 3-5 parts of a water-based binder, 1-2 parts of a conductive agent and deionized water; the viscosity of the aqueous positive electrode slurry is 3000mPa & s-6000mPa & s.

2. The aqueous positive electrode slurry for the lithium iron phosphate battery as claimed in claim 1, wherein the composite graphene conductive slurry comprises the following raw materials in parts by weight: 3-5 parts of carbon nano tube, 1.0-1.5 parts of graphene, 0.8-1.2 parts of dispersing agent and 92-94 parts of deionized water.

3. The aqueous positive electrode slurry for lithium iron phosphate batteries according to claim 1, wherein the aqueous binder comprises an acrylonitrile multipolymer.

4. The aqueous positive electrode paste for lithium iron phosphate batteries according to claim 1, wherein the conductive agent comprises one or more of conductive carbon black, acetylene black, carbon fibers, carbon nanotubes, and ketjen black.

5. The aqueous positive electrode slurry for lithium iron phosphate batteries according to claim 1, wherein the deionized water has an electrical conductivity of 1 μ s/cm or less.

6. A method for preparing an aqueous positive electrode slurry for a lithium iron phosphate battery according to any one of claims 1 to 5, comprising the steps of:

s1, mixing the composite graphene conductive slurry, the water-based binder and deionized water, stirring and gluing to obtain mixed slurry;

s2, kneading and stirring the lithium iron phosphate and the conductive agent to obtain mixed powder;

s3, mixing the mixed powder and the mixed slurry, stirring at a low speed and then at a high speed to obtain a mixture;

and S4, adding deionized water into the mixture, and stirring at a high speed to obtain the water-based positive electrode slurry with the viscosity of 3000-6000 mPa & S.

7. The method according to claim 6, wherein in step S1, the revolution of stirring and gluing is 20 to 30rmp, and the dispersion rotation speed is 2500 to 4000 rmp; the stirring time is 60-120 min.

8. The method according to claim 6, wherein in step S1, the deionized water has a conductivity of 1 μ S/cm or less; the solid content of the obtained mixed slurry is 45-65 wt%.

9. The production method according to claim 6, wherein in step S2, the revolution of kneading and stirring is 15 to 30rmp, and the dispersion rotation speed is 1500 to 3000 rmp; the stirring time is 180-240 min.

10. The production method according to claim 6, wherein in step S3, the revolution of the low-speed stirring is 12 to 18rmp, the revolution of the high-speed stirring is 20 to 50rmp, and the dispersion rotation speed is 2000 to 4500 rmp; the stirring time is 60-150 min.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a water-based cathode slurry of a lithium iron phosphate battery and a preparation method thereof.

Background

The lithium iron phosphate material has the advantages of rich raw material sources, environmental protection, no toxicity, high working voltage, good thermal stability and the like, and is considered to be an ideal anode material of a new generation of lithium ion batteries. The lithium iron phosphate battery is a lithium ion battery using lithium iron phosphate as a positive electrode material, and a positive electrode slurry of the lithium ion battery contains an active material, a conductive agent, a binder, a solvent and the like in addition to the positive electrode material. The lithium iron phosphate lithium ion battery has the advantages of high power density, long cycle life, good safety performance, environmental friendliness and the like, so that the lithium iron phosphate lithium ion battery has wide application prospect in the technical field of power. The lithium iron phosphate power battery IC is used for 2000 times in a discharging way, and the capacity retention rate is not lower than 80%. Because the power battery has higher and higher requirements on the rate performance, the performance requirements of the lithium iron phosphate material are improved, the particles are refined and even nanocrystallized, and in order to meet the use requirements of the power battery and solve the problem of high-rate discharge of the lithium ion battery, a lithium iron phosphate battery with high-rate discharge and long cycle life needs to be developed.

The aqueous composite graphene conductive agent is a newly-developed conductive agent in recent years, generally has a diameter of about 3-5 nanometers and a length of 10-30 micrometers, can serve as a lead in a conductive network, and has an electric double layer effect to play a high-rate characteristic of a lithium ion battery; in addition, the good heat-conducting property of the composite graphene conductive paste is beneficial to fast heat dissipation of the lithium battery during charging and discharging, the polarization internal resistance of the battery is reduced, the high and low temperature performance of the battery is improved, the service life of the battery is prolonged, and the components of the aqueous composite graphene conductive paste are graphene, carbon nano tubes, a dispersing agent and deionized water, and do not contain a toxic substance NMP

In addition, NMP is adopted as a solvent for slurry in the existing lithium iron phosphate lithium ion battery positive electrode pulping process. However, NMP is volatile, flammable and explosive, and has high toxicity, so that the environment is easily polluted seriously, the toxicity of a production field is high, and the physical health of workers in a production workshop is seriously influenced. However, the aqueous composite graphene conductive paste has a large specific surface area, is easy to agglomerate and is not easy to uniformly disperse in a solvent.

Disclosure of Invention

The invention aims to provide a water-based positive electrode slurry of a lithium iron phosphate battery with good dispersion and high stability and a preparation method thereof.

The technical scheme adopted by the invention for solving the technical problems is as follows: the water-based positive electrode slurry of the lithium iron phosphate battery comprises the following raw materials in parts by weight: 90-93 parts of lithium iron phosphate, 2-3 parts of composite graphene conductive slurry, 3-5 parts of a water-based binder, 1-2 parts of a conductive agent and deionized water; the viscosity of the aqueous positive electrode slurry is 3000mPa & s-6000mPa & s.

Preferably, the composite graphene conductive paste comprises the following raw materials in parts by weight: 3-5 parts of carbon nano tube, 1.0-1.5 parts of graphene, 0.8-1.2 parts of dispersing agent and 92-94 parts of deionized water.

Preferably, the aqueous binder comprises an acrylonitrile multipolymer.

Preferably, the conductive agent comprises one or more of conductive carbon black, acetylene black, carbon fiber, carbon nanotube, and ketjen black.

Preferably, the conductivity of the deionized water is less than or equal to 1 mu s/cm

The invention also provides a preparation method of the water-based positive electrode slurry of the lithium iron phosphate battery, which comprises the following steps of:

s1, mixing the composite graphene conductive slurry, the water-based binder and deionized water, stirring and gluing to obtain mixed slurry;

s2, kneading and stirring the lithium iron phosphate and the conductive agent to obtain mixed powder;

s3, mixing the mixed powder and the mixed slurry, stirring at a low speed and then at a high speed to obtain a mixture;

and S4, adding deionized water into the mixture, and stirring at a high speed to obtain the water-based positive electrode slurry with the viscosity of 3000-6000 mPa & S.

Preferably, in step S1, the revolution of stirring and glue-beating is 20-30 rmp, and the dispersion rotation speed is 2500-4000 rmp; the stirring time is 60-120 min.

Preferably, in step S1, the conductivity of the deionized water is less than or equal to 1 μ S/cm; the solid content of the obtained mixed slurry is 45-65 wt%.

Preferably, in step S2, the revolution of kneading and stirring is 15 to 30rmp, and the dispersion rotation speed is 1500 to 3000 rmp; the stirring time is 180-240 min.

Preferably, in step S3, the revolution of low-speed stirring is 12 to 18rmp, the revolution of high-speed stirring is 20 to 50rmp, and the dispersion rotation speed is 2000 to 4500 rmp; the stirring time is 60-150 min.

According to the water-based positive electrode slurry of the lithium iron phosphate battery, deionized water is used as a dispersion medium, so that the dispersibility of the water-based positive electrode slurry is improved, the environmental pollution caused by the use of an organic solvent is avoided, and the water-based positive electrode slurry is more environment-friendly and safer; in the components of the aqueous positive electrode slurry, the contents of a conductive agent and an aqueous binder are optimized, and meanwhile, the aqueous graphene composite conductive slurry is used as the conductive agent, so that the ohmic internal resistance and the polarization internal resistance of the battery can be reduced, and the high-power starting performance of the lithium battery is improved.

According to the preparation method of the water-based cathode slurry, dry stirring is adopted, the dispersibility of the slurry is good, the conductivity of the slurry is improved, the internal resistance of a battery is further reduced, and the rate capability is improved. In addition, compared with other stirring modes, the slurry has low viscosity under the condition of the same solid content, and the processing performance of the slurry is effectively improved.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a discharge rate discharge graph of example 1 of the present invention;

FIG. 2 is a discharge rate discharge graph of example 2 of the present invention;

FIG. 3 is a discharge rate discharge curve diagram of example 3 of the present invention.

Detailed Description

The invention relates to a water-based positive electrode slurry of a lithium iron phosphate battery, which comprises the following raw materials in parts by weight: 90-93 parts of lithium iron phosphate, 2-3 parts of composite graphene conductive slurry, 3-5 parts of a water-based binder and 1-2 parts of a conductive agent; the composite material also comprises deionized water which is used as a dispersion medium to replace the traditional NMP, so that the generation of pollution gas in the manufacturing process is reduced.

The viscosity of the aqueous positive electrode slurry of the present invention is 3000mPa · s to 6000mPa · s, and an appropriate amount of deionized water is added to achieve the viscosity. The conductivity of the deionized water is less than or equal to 1 mu s/cm, and the self-discharge probability of the battery caused by metal impurities in the deionized water is reduced.

In the aqueous positive electrode slurry of the present invention, lithium iron phosphate is a positive electrode active material; the conductive agent imparts conductivity to the aqueous positive electrode slurry. Alternatively, the conductive agent includes one or more of conductive carbon black, acetylene black, carbon fiber (VGCF), Carbon Nanotubes (CNTs), ketjen black. The conductive carbon black can be selected from Super P and Super S; ketjenblack may be selected from Ketjenblack EC300J, Ketjenblack EC600JD, Carbon ECP, and Carbon ECP600 JD.

The composite graphene conductive slurry also has a conductive effect, and can be filled in gaps between conductive agents and between the conductive agents and lithium iron phosphate in aqueous anode slurry, so that the gaps between the conductive agents and the lithium iron phosphate are eliminated or reduced, the ohmic internal resistance and the polarization internal resistance of the battery can be reduced, and the high-power starting performance of the battery is improved. The composite graphene conductive slurry comprises the following raw materials in parts by weight: 3-5 parts of carbon nano tube, 1.0-1.5 parts of graphene, 0.8-1.2 parts of dispersing agent (PVP) and 92-94 parts of deionized water. Preferably, the composite graphene conductive paste includes: 4 parts of carbon nano tube, 1.2 parts of graphene, 1 part of dispersing agent and 93.8 parts of deionized water.

The aqueous binder comprises an acrylonitrile multipolymer.

The preparation method of the water-based positive electrode slurry of the lithium iron phosphate battery can comprise the following steps of:

s1, mixing the composite graphene conductive slurry, the water-based binder and deionized water, stirring and gluing to obtain mixed slurry.

The water-based adhesive adopts water-based adhesive prepared from acrylonitrile multipolymer, wherein the acrylonitrile multipolymer is used as solute in the water-based adhesive, and the content of the acrylonitrile multipolymer accounts for 16 wt% of the total amount of the water-based adhesive. The conductivity of the added deionized water is less than or equal to 1 mu s/cm, and the addition amount of the deionized water is based on that the solid content of the obtained mixed slurry is 45-65 wt%.

The revolution of stirring and glue beating is 20-30 rmp, and the dispersion rotating speed is 2500-4000 rmp. The stirring time is 60-120 min.

And S2, kneading and stirring the lithium iron phosphate and the conductive agent to obtain mixed powder.

The revolution of kneading and stirring is 15-30 rmp, and the dispersion rotating speed is 1500-3000 rmp; the stirring time is 180-240 min.

And S3, mixing the mixed powder and the mixed slurry, stirring at a low speed and then at a high speed to obtain a mixture.

Wherein the revolution of low-speed stirring is 12-18 rmp, the revolution of high-speed stirring is 20-50 rmp, and the dispersion rotating speed is 2000-4500 rmp; the stirring time is 60-150 min.

And S4, adding deionized water into the mixture, and stirring at a high speed to obtain the water-based positive electrode slurry with the viscosity of 3000-6000 mPa & S.

In the obtained aqueous positive electrode slurry, the acrylonitrile multipolymer accounts for 1.5 to 3.5 weight percent of all solid contents.

The invention is further illustrated by the following specific examples.

Example 1

(1) 1041.6g of aqueous adhesive ADY-701A (the solid content is 16 wt%), 485g of water used as a solvent and 1587g of composite graphene conductive slurry (the solid content is 6.3 wt%) are mixed, and the mixture is placed into a Guangzhou Hongtong mixer to be mixed for 100min at the revolution speed of 25rpm/min and the dispersion speed of 2500 rpm/min; the viscosity was measured to be 3500 mPas.

(2) 3000g of lithium iron phosphate active material and 66.6g of conductive agent SP are added into a Guangzhou Senhong mixer and then mixed for 180min at the revolution speed of 15rpm/min and the dispersion speed of 1500 rpm/min.

(3) And then adding the stirred glue solution in the step (1) into the kneaded powder in the step (2) for two-stage addition and stirring: 622.9g of glue solution (1) with the weight ratio of 20 percent is added, the slurry is stirred for 30min at the revolution speed of 15rpm/min and the dispersion speed of 1500rpm/min to achieve the effect of pre-dispersing mud, then 2491.5g of glue solution (1) with the weight ratio of 80 percent is added, the mixture is stirred for 120min at the revolution speed of 50rpm/min and the dispersion speed of 3000rpm/min, and the solid content of the stage is 53.8 percent.

(4) 485.5g of water is added into the product in the step (3), and the mixture is stirred at a high speed of revolution speed of 35rpm/min and dispersion speed of 2500rpm/min for 45min to prepare the water-based positive electrode slurry with the final solid content of 50.4% and the viscosity of 4300 mPas.

Lithium iron phosphate battery 805875-2.0Ah 1C charge was prepared using the aqueous positive electrode slurry of this example, and the discharge rate curves at 30C, 35C, and 40C are shown in FIG. 1 (at room temperature).

Example 2

(1) 815.2g of ADY-701A (solid content is 16 wt%), 385.3g of water used as a solvent and 1294g of composite graphene conductive slurry (solid content is 6.3 wt%) are mixed, and the mixture is put into a Guangzhou Hongtong mixer to be mixed for 100min at a revolution speed of 25rpm/min and a dispersion speed of 2500 rpm/min; the viscosity was found to be 3400 mPas.

(2) 3000g of lithium iron phosphate active material and 48.9g of conductive agent SP are added into a Senhong mixer and then stirred for 180min at the revolution speed of 15rpm/min and the dispersion speed of 1500 rpm/min.

(3) Adding the stirred glue solution in the step (1) into the kneaded powder in the step (2) for two-stage addition and stirring: 499g of glue solution with the weight ratio of 20 percent is added firstly, the effect of pre-dispersing mud is achieved by stirring the slurry for 30min at the revolution speed of 15rpm/min and the dispersion speed of 1500rpm/min, then 1995.6g of glue solution with the weight ratio of 80 percent of (1) is added, the slurry is stirred for 120min at the revolution speed of 50rpm/min and the dispersion speed of 3000rpm/min, and the solid content of the stage is 58.8 percent.

(4) 385.3g of water was added to the product of (3), and the mixture was stirred at a revolution speed of 35rpm/min and a dispersion speed of 2500rpm/min for 45min to obtain an aqueous positive electrode slurry having a final solid content of 55.1% and a viscosity of 5300 mPas.

Lithium iron phosphate battery 805875-2.0Ah 1C charge was prepared using the aqueous positive electrode slurry of this example, and the discharge rate curves at 30C, 35C, and 40C are shown in FIG. 2 (at room temperature).

Example 3

(1) 604.8g of ADY-701A (solid content is 16 wt%), 919g of water as a solvent and 1536g of composite graphene conductive paste (solid content is 6.3 wt%) are mixed, and the mixture is put into a Guangzhou Hongtong mixer to be mixed for 100min at the revolution speed of 26rpm/min and the dispersion speed of 2600 rpm/min; the viscosity was found to be 3600 mPas.

(2) 3000g of lithium iron phosphate active material and 32.35g of conductive agent SP are added into a Guangzhou Senhong mixer and then mixed for 180min at the revolution speed of 15rpm/min and the dispersion speed of 1500 rpm/min.

(3) Adding the stirred glue solution in the step (1) into the kneaded powder in the step (2) for two-stage addition and stirring: firstly, 612g of the total amount of 20 percent of the weight of the glue solution of (1) is added, the slurry is stirred for 30min at the revolution speed of 15rpm/min and the dispersion speed of 1500rpm/min to achieve the effect of pre-dispersing mud, then 2448g of the total amount of 80 percent of the weight of the glue solution of (1) is added, the high-speed stirring is carried out for 120min at the revolution speed of 50rpm/min and the dispersion speed of 3300rpm/min, and the solid content of the stage is 52.9 percent.

(4) And 919g of water is added into the product in the step (3), and the mixture is stirred at a high speed of 35rpm/min of revolution speed and 2600rpm/min of dispersion speed for 45min to prepare the water-based positive electrode slurry with the final solid content of 46.5% and the viscosity of 4300 mPas.

Lithium iron phosphate battery 805875-2.0Ah 1C charge was prepared using the aqueous positive electrode slurry of this example, and the discharge rate curves at 30C, 35C, and 40C are shown in FIG. 3 (at room temperature).

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.