CN111697225A - Lithium iron phosphate anode slurry for lithium ion battery, preparation method of lithium iron phosphate anode slurry and anode plate - Google Patents
Lithium iron phosphate anode slurry for lithium ion battery, preparation method of lithium iron phosphate anode slurry and anode plate Download PDFInfo
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Abstract
The invention discloses lithium iron phosphate anode slurry for a lithium ion battery, a preparation method of the lithium iron phosphate anode slurry and an anode plate, and belongs to the field of lithium ion batteries. The positive electrode slurry comprises 93-97 parts of lithium iron phosphate positive electrode active material, 2-5 parts of binder and 1-3 parts of conductive agent, wherein the specific surface area of the lithium iron phosphate positive electrode active material is 6-12 m2The adhesive contains acrylate multipolymer with the degree of substitution of 0.73-3.0; the preparation method comprises the steps of fully mixing the conductive agent with equal mass and the binder to form a conductive glue solution, wherein the pH value of the conductive glue solution is 8-11, and thenAnd adding a lithium iron phosphate positive active material and a binder, fully stirring and dispersing in the conductive glue solution, and finally defoaming and adjusting the viscosity to obtain the lithium iron phosphate positive slurry for the lithium ion battery. The components in the anode slurry are uniformly dispersed, and do not settle, so that the use standard of the electrode is met.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to lithium iron phosphate anode slurry for a lithium ion battery, a preparation method of the lithium iron phosphate anode slurry and an anode pole piece.
Background
The positive electrode slurry is one of the main parts of the lithium ion battery structure, and the quality of the battery test result depends on the self-characteristics of the positive electrode raw material. The determination of the positive electrode slurry has a high standard for the raw material itself, and the conditions are as follows: (1) the lithium ions move back and forth in the charging and discharging process, which has certain influence on the volume, so that the lithium ion battery has a layered or tunnel structure, and the volume of the lithium ions is not greatly changed during the insertion and the extraction; (2) the redox reaction of the lithium ions occurs in the back-and-forth de-intercalation process, and the redox potential of the selected material is almost close to that of the lithium ions; (3) the de-intercalation is a reversible process, the density of high capacity has reversible high capacity, and the material must have high reversibility; (4) as the content of lithium ions decreases, less lithium alloy is generated, and the redox potential also decreases as much as possible, so that the battery has a smooth charge and discharge voltage.
In the manufacturing process of the electrode of the lithium ion battery, the positive electrode slurry consists of a binder, a conductive agent, an active material, an additive and the like, and the preparation of the positive electrode slurry comprises a series of processes of mixing, dissolving, dispersing and the like between liquid and between liquid and solid materials, and the processes are accompanied by changes of temperature, viscosity, environment and the like. In the positive electrode slurry, the dispersibility and uniformity of the granular active substances directly affect the movement of lithium ions between two electrodes of the battery, so that the mixing and dispersion of the slurry of each pole piece material in the production of the lithium ion battery are very important, and the quality of the dispersion of the slurry directly affects the quality of the subsequent production of the lithium ion battery and the performance of the product thereof.
The existing lithium iron phosphate homogenizing process has the defects that the particle size of the particle positive electrode active material is small and the specific surface area is large, so the particle positive electrode active material is difficult to disperse and easy to block during sieving, and the coating process is easy to cause foil exposure and marking, and slurry is easy to settle.
Through retrieval, Chinese patent application No. 201910741166.1, and patent application publication number 2019, 10 and 8 disclose a preparation method of a lithium ion battery aqueous binder cathode slurry. The positive electrode slurry comprises a positive electrode active substance, a conductive agent, a water-based binder, a dispersing agent and deionized water, wherein the water-based binder is acrylate glue, raw materials are selected according to components in the positive electrode slurry, the positive electrode active substance, the conductive agent and a solid dispersing agent are respectively ground into powder, the positive electrode active substance is lithium iron phosphate, the dispersing agent is used for replacing N-methyl pyrrolidone (NMP) as a dispersing solvent, the dispersing agent is one or a plurality of mixtures, and the dispersing efficiency is improved; secondly, in the proportion of the water-based binder, the acrylic ester adhesive used in the invention has weaker binding effect.
For another example, a patent application with chinese patent application No. 201611180954.0 and published as 2017, 5 and 31 discloses a lithium iron phosphate cathode slurry and a preparation method thereof. The patent anode slurry comprises the following components in parts by weight: 95-97% of active material lithium iron phosphate, 0.5-2% of conductive agent and 1-3% of binder PVDF, wherein the conductive agent is a mixture of carbon nanotubes and graphene, and the weight ratio of the carbon nanotubes to the graphene is (4-7) to (3-6). The anode slurry is used for a mixed pulping process, and the preparation method comprises the following steps: firstly, dry-mixing the active material, the conductive agent and the binder, then adding the organic solvent to stir and mix evenly, and finally vacuumizing, reversing and defoaming. However, the effect of this invention on the dispersion of lithium iron phosphate is weak; the PVDF is used as a binder, so that the internal resistance of the whole positive pole piece is obviously higher, the heat generation ratio is higher and the internal consumption is higher in the process of carrying out high-rate charge and discharge on the battery cell; in addition, the invention uses the mixed conductive slurry of the carbon nanotubes and the graphene as the conductive agent, although the conductive agent has certain advantages in conductivity, the carbon nanotubes are easy to settle, and the dispersibility is poor; finally, the invention still uses NMP as solvent, which is a big problem in terms of environmental protection and economy.
Disclosure of Invention
1. Problems to be solved
Aiming at the problem that the lithium iron phosphate active substance in the existing lithium iron phosphate anode slurry is not easy to disperse, the invention provides the lithium iron phosphate anode slurry, by optimizing the anode slurry formula, the components in the anode slurry are uniformly dispersed without sedimentation, and the performance of the slurry is ensured to meet the use standard of the anode slurry of the lithium ion battery.
The invention also provides a preparation method of the lithium iron phosphate anode slurry, and aims to improve the dispersibility of the anode slurry.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the lithium iron phosphate anode slurry for the lithium ion battery comprises a lithium iron phosphate anode active material, a binder and a conductive agent, wherein the lithium iron phosphate anode active material comprises the following components in parts by mass:
93-97 parts of lithium iron phosphate positive active material;
2-5 parts of a binder;
1-3 parts of a conductive agent;
wherein the specific surface area of the lithium iron phosphate positive electrode active material is 6-12 m2The adhesive contains acrylate multipolymer with the degree of substitution of 0.73-3.0.
Further, the particle size distribution of the lithium iron phosphate positive electrode active material is D10: 0-1 micron, D50: 1-2 microns, D90 not more than 5 microns, and tap density of 0.8-1.2 g/cm3Wherein "D10: 0 to 1 μm "indicates that the cumulative particle size distribution percentage of lithium iron phosphate reaches 10%, and the corresponding particle diameter is 0 to 1 μm," D50: 1-2 microns "indicates the accumulation of lithium iron phosphateThe corresponding particle size is 1-2 microns when the percentage of the calculated particle size distribution reaches 50 percent, and the D90 is less than or equal to 5 microns indicates that the corresponding particle size is less than or equal to 5 microns when the percentage of the accumulated particle size distribution of the lithium iron phosphate reaches 90 percent.
Further, the acrylate multipolymer accounts for 25-50% of the total mass of the adhesive.
Further, the binder is a mixture of acrylate multipolymer and polyacrylic resin emulsion.
Further, the acrylate multipolymer is dissolved in an aqueous solution, the pH value of the acrylate multipolymer is 6-8, the viscosity of the acrylate multipolymer is 1500-5000 mPa.S, and the acrylate multipolymer in the acrylate multipolymer solution is 15%.
Further, the conductive agent is carbon black (SP), and the specific surface area of medium particles is 55-65 m2/g。
A preparation method of lithium iron phosphate anode slurry of a lithium ion battery comprises the following steps: fully mixing a conductive agent with equal mass and a binder to form a conductive glue solution, wherein the pH of the conductive glue solution is 8-11, then adding a lithium iron phosphate positive active substance and the binder, fully stirring and dispersing in the conductive glue solution, and finally defoaming and adjusting the viscosity to obtain the lithium iron phosphate positive slurry for the lithium ion battery.
Specifically, the preparation method of the lithium iron phosphate anode slurry of the lithium ion battery comprises the following steps:
(1) preparing a conductive glue solution: fully stirring and dispersing the binder and the conductive agent with equal mass, wherein the stirring speed is 40-50 rpm, the dispersion speed is 4000-5000 rpm, and the stirring time is 150-210 min to obtain a conductive glue solution, wherein the pH value of the conductive glue solution is 8-11; wherein, the stirring and the dispersing are respectively carried out by a large dispersion plate and a small dispersion plate at the same time;
(2) dispersion of lithium iron phosphate positive electrode active material: adding a binder and a lithium iron phosphate positive electrode active substance into the conductive glue solution together, stirring and dispersing in two steps, wherein the stirring speed in the first step is 15-25 rpm, and the stirring time is 25-35 min; after scraping, the stirring speed in the second step is 25-35 rpm, the dispersion speed is 2500-3500 rpm, and the stirring time is 100-140 min; wherein, the stirring and the dispersing are respectively carried out by a large dispersion plate and a small dispersion plate at the same time;
(3) and (3) reverse defoaming: the stirring speed is-20 to-30 rpm, and the stirring time is 25 to 35 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery.
Further, the step (4) adopts the addition of deionized water to adjust the viscosity of the slurry.
Further, in the preparation method, a high-speed centrifugal defoaming stirrer is used for stirring and dispersing.
A positive pole piece is prepared by coating the positive pole slurry.
A lithium ion battery comprises the positive pole piece.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) the lithium iron phosphate anode active material has the characteristics of small particle size, large specific surface area and the like, has relatively large surface energy, is easy to have the conditions of uneven dispersion and particle agglomeration and sedimentation in the preparation process of the slurry, and makes the preparation of the anode slurry become a big difficulty, which is the problem, so that the research and development of the lithium ion battery cannot be broken through2When the polymer network structure is used for preparing the lithium iron phosphate positive active material particles, the dispersion speed is high in the preparation process of the slurry, the slurry density is uniform, and the possible reason for analysis is that the acrylate with large molecular weight and high substitution degree has high viscosity, and the adsorption capacity of the acrylate on the surfaces of the lithium iron phosphate positive active material particles is increased, so that an effective polymer network structure is formed, and the lithium iron phosphate positive active material particles are uniformly dispersed; in particular, when the degree of substitution A of the acrylic ester is less than 0.73, the cohesive force in the whole acrylic ester system is greatly lowered, the fluidity is too good, andthe kneading and bonding of the sizing agent have negative effect; the substitution degree A of the acrylic ester is higher than 3.0, the flowability is too poor, the whole slurry system is more difficult to process, and the advantage of a water-based adhesive system is not provided;
(2) the lithium iron phosphate anode of the lithium ion battery has the particle size of an active material of the lithium iron phosphate anode of D10: 0-1 micron, D50: 1-2 microns, D90 not more than 5 microns, and the specific surface area of the material is 6-12 m2(iv) g, tap density of 0.8-1.2 g/cm3(ii) a On one hand, the specific surface area of the lithium iron phosphate active material is ensured to meet the requirement by controlling the particle size, and on the other hand, the acrylate and the lithium iron phosphate positive active material can generate a synergistic effect by the effective combination of the three, so that the dispersibility is better;
(3) the invention adopts the mixture of the acrylate multipolymer and the polyacrylic resin emulsion as the adhesive, on one hand, the invention is a water-based adhesive, and has the advantages of more environmental protection and economy on the aspect of water-based processing conditions; on the other hand, the amount of the acrylate multipolymer is slightly less than that of the polyacrylic resin emulsion, because the surface of the acrylate multipolymer is inevitably accompanied with residual alkaline substances in the preparation process, and the addition of the acrylate multipolymer into the positive electrode slurry can increase the internal resistance of the battery and influence the performance of the battery; although the polyacrylic acid resin emulsion is not as good as acrylate in adhesion, the effect on the flexibility and tension of the pole piece is very beneficial to the processing of the pole piece;
(4) the pH value of the acrylate multipolymer is controlled to be 6-8, the viscosity is 1500-5000 mPa.S, and the acrylate multipolymer has the advantages of low viscosity and easy dispersion processing; controlling the specific surface area of the conductive agent carbon black (SP) to be 55-65 m2The advantages of the material are that the conductivity of the pole piece can be improved to the maximum extent;
(5) the invention relates to a preparation method of a lithium ion battery lithium iron phosphate anode, which comprises the steps of adding a binder in two steps, wherein the most important step is a first step which comprises the amount of the added glue solution and a stirring mode, and a proper amount of acrylate glue solution (namely the binder) is added in the first step to ensure that a conductive agent is fully mixed with the acrylate glue solution material and is subjected to strong shearing stirring, so that fine particles of flowing slurry are fully and uniformly mixed within enough time (conductive glue solution); then adding another part of the acrylate glue solution to be mixed and dispersed (fine mixing) with the main material;
(6) according to the preparation method of the lithium iron phosphate anode of the lithium ion battery, on the premise that the slurry is fully mixed and stirred, high-speed stirring and defoaming are carried out at last, and finally the viscosity of the slurry can be adjusted along with the amount of deionized water;
(7) the preparation method of the lithium iron phosphate anode of the lithium ion battery has the advantages of simple operation, controllable time, good slurry preparation mixing effect, good stability, dispersibility and coating performance of the lithium iron phosphate anode, flat surface of a coated pole piece, no agglomerated particles and high peel strength, so that the current distribution of the pole piece is uniform in the charging and discharging process, the lithium iron phosphate cathode battery has high initial efficiency and few scattered points, and good cycle, multiplying power and electrode dynamic performance are shown.
Drawings
Fig. 1 is an external view of a positive electrode paste according to the present invention;
FIG. 2 is a diagram of a positive electrode sheet coated with the positive electrode slurry of the present invention;
FIG. 3 is a particle size distribution diagram of DY-3 lithium iron phosphate.
Detailed Description
The invention is further described with reference to specific examples.
Table 1 shows the raw material information used in the examples.
Table 1 raw material information
| Name of raw material | Manufacturer information | Model number |
| Lithium iron phosphate | German square nanometer | DY-3 |
| Acrylate multipolymer | Blue sea black stone | BA-306F-TDS V2 |
| Polyacrylic resin emulsion | Blue sea black stone | BA-405M-V1 |
| PVDF | Suwei | 5130 |
| SP | Temi high, Switzerland Co Ltd | SP-Li |
It is to be noted that the particle size distribution of DY-3 lithium iron phosphate used in the embodiment is shown in FIG. 3, and D10:0.50 μm, D50:1.14 μm, D90:9.10 μm, D97:4.46 μm, and D99:5.41 μm can be obtained.
TABLE 2 raw material parameters and formulations for the examples
It should be noted that different specific surface areas can be controlled by controlling the sintering temperature and atmosphere of LFP (lithium iron phosphate), for example, in the same batch, the sintering condition at the periphery of the crucible is poor, so LFP (lithium iron phosphate) with different specific surface areas can be used in the embodiment of the present invention and the comparative example, and the lithium iron phosphate with different specific surface areas in the embodiment can be directly selected from products with corresponding specific surface areas.
Example 1
The lithium iron phosphate cathode slurry for the lithium ion battery in the embodiment has the following formula (the components are calculated by mass parts):
lithium iron phosphate (specific surface area of 8.68 m)2/g) 93 parts;
2 parts of 15 percent acrylate multipolymer solution (the degree of substitution is 1.73);
3 parts of polyacrylic resin emulsion;
2 parts of SP-Li;
wherein the tap density of the lithium iron phosphate is 0.92g/cm3(ii) a The pH of a 15% acrylate multipolymer solution was 6.86, the viscosity was 2340 mPaS; the specific surface area of SP-Li is 58m2(ii)/g; when in use, 2 parts of 15 percent acrylate multipolymer solution and 3 parts of polyacrylic resin emulsion are mixed into the adhesive.
According to the formula, the preparation method of the lithium iron phosphate anode slurry for the lithium ion battery comprises the following steps:
(1) preparing a conductive glue solution: respectively taking 2 parts of binder and 2 parts of SP-Li, fully mixing, stirring and dispersing by using a high-speed centrifugal defoaming stirrer at a stirring speed of 45rpm and a dispersing speed of 4500rpm for 180min to obtain a conductive glue solution, wherein the pH value of the conductive glue solution is 9.03;
(2) dispersion of lithium iron phosphate positive electrode active material: adding 3 parts of binder and 93 parts of lithium iron phosphate positive active material into the conductive glue solution obtained in the step (1) together, and stirring and dispersing in two steps, wherein the stirring speed in the first step is 20rpm, and the stirring time is 30 min; after scraping, the stirring speed of the second step is 30rpm, the dispersion speed is 3000rpm, and the stirring time is 120 min;
(3) and (3) reverse defoaming: stirring at-25 rpm for 30 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate cathode slurry of the lithium ion battery.
Example 2
The lithium iron phosphate cathode slurry for the lithium ion battery in the embodiment has the following formula (the components are calculated by mass parts):
lithium iron phosphate (specific surface area of 8.52 m)2Per gram) 95 parts;
1 part of 15 percent acrylate multipolymer solution (the degree of substitution is 1.73);
3 parts of polyacrylic resin emulsion;
1 part of SP-Li;
wherein the tap density of the lithium iron phosphate is 0.93g/cm3(ii) a The pH of a 15% acrylate multipolymer solution was 6.86, the viscosity was 2340 mPaS; the specific surface area of SP-Li is 58m2(ii) in terms of/g. When in use, 1 part of 15 percent acrylate multipolymer solution and 3 parts of polyacrylic resin emulsion are mixed into the adhesive.
The preparation method of the lithium iron phosphate anode slurry for the lithium ion battery comprises the following steps:
(1) preparing a conductive glue solution: fully mixing 1 part of binder and 1 part of conductive agent, stirring and dispersing by using a high-speed centrifugal defoaming stirrer at a stirring speed of 40rpm for 150min to obtain a conductive glue solution; wherein the pH value of the conductive glue solution is 9.03;
(2) dispersion of lithium iron phosphate positive electrode active material: adding 3 parts of binder and 95 parts of lithium iron phosphate positive electrode active material into the conductive glue solution obtained in the step (1) together for mixing and dispersing, wherein the first-step stirring speed is 15rpm, the dispersing speed is 0, and the stirring time is 25 min; after scraping, the stirring speed in the second step is 25rpm, the dispersion speed is 2500rpm, and the stirring time is 100 min;
(3) defoaming: the stirring speed is-20 rpm, the dispersion speed is 0, and the stirring time is 30 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery.
Example 3
The lithium iron phosphate cathode slurry for the lithium ion battery in the embodiment has the following formula (the components are calculated by mass parts):
lithium iron phosphate (specific surface area of9.03m2/g) 97 parts;
1 part of 15 percent acrylate multipolymer solution (the degree of substitution is 1.73);
1 part of polyacrylic resin emulsion;
1 part of SP-Li;
wherein the tap density of the lithium iron phosphate is 0.92g/cm3(ii) a The pH of a 15% acrylate multipolymer solution was 6.86, the viscosity was 2340 mPaS; the specific surface area of SP-Li is 58m2Per g, pH 9.03. When in use, 1 part of 15 percent acrylate multipolymer solution and 1 part of polyacrylic resin emulsion are mixed into the adhesive.
The preparation method of the lithium iron phosphate anode slurry for the lithium ion battery comprises the following steps:
(1) preparing a conductive glue solution: fully mixing 1 part of adhesive and 1 part of conductive agent, stirring and dispersing by using a high-speed centrifugal defoaming stirrer at a stirring speed of 50rpm for 210min to obtain a conductive adhesive solution, wherein the dispersion speed is 5000 rpm; wherein the pH value of the conductive glue solution is 9.03;
(2) dispersion of lithium iron phosphate positive electrode active material: adding 1 part of binder and 97 parts of lithium iron phosphate positive active material into the conductive glue solution together for mixing and dispersing, wherein the stirring speed in the first step is 25rpm, the dispersing speed is 0, and the stirring time is 35 min; after scraping, the stirring speed in the second step is 35rpm, the dispersion speed is 3500rpm, and the stirring time is 140 min;
(3) defoaming: vacuum of-0.08 to-0.1 MPa, stirring speed of-30, dispersion speed of 0 and stirring time of 35 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery.
Comparative example 1
The formula of the lithium iron phosphate anode slurry for the comparative example is as follows (the components are calculated by mass portions):
95 parts of lithium iron phosphate (the specific surface area is 8.52);
1 part of PVDF;
1 part of SP-Li;
wherein the tap density of the lithium iron phosphate is 0.93g/cm3(ii) a The specific surface area of SP-Li is 58m2Per g, pH 9.03.
(1) Preparing PVDF conductive glue solution: fully mixing 1 part of PVDF binder and 1 part of NMP, stirring and dispersing by using a high-speed centrifugal defoaming stirrer at the stirring speed of 45rpm for 240min to obtain PVDF glue solution, wherein the dispersion speed is 4500 rpm; adding 1 part of conductive agent SP-LI, stirring at 45rpm, dispersing at 4500rpm, and stirring for 120min to obtain PVDF conductive glue solution;
(2) dispersion of lithium iron phosphate positive electrode active material: adding 95 parts of lithium iron phosphate positive active material into PVDF conductive glue solution for mixing and dispersing, wherein the first-step stirring speed is 20rpm, the dispersing speed is 0rpm, and the stirring time is 30 min; after scraping, the stirring speed of the second step is 20rpm, the dispersion speed is 2500rpm, and the stirring time is 60 min; after scraping, the final stirring speed is 45rpm, the dispersion speed is 4500rpm, and the stirring time is 120 min;
(3) defoaming: the stirring speed is-25 rpm, the dispersion speed is 0rpm, and the stirring time is 30 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery in the comparative example 1.
Comparative example 2
The lithium iron phosphate anode slurry for the lithium ion battery in the comparative example has the following formula (the components are calculated in parts by mass):
lithium iron phosphate (specific surface area of 8.52 m)2Per gram) 95 parts;
1 part of 15 percent acrylate multipolymer solution (with the degree of substitution of 0.48);
3 parts of polyacrylic resin emulsion;
1 part of SP-Li;
wherein the tap density of the lithium iron phosphate is 0.93g/cm3(ii) a The pH of a 15% acrylic ester multipolymer solution was 8.11, and the viscosity was 4860 mPaS; the specific surface area of SP-Li is 58m2Per g, pH 9.03. When in use, 1 part of 15 percent acrylate multipolymer solution and 3 parts of polyacrylic resin emulsion are mixedThe liquids are mixed into a binder.
(1) Preparing a conductive glue solution: fully mixing 1 part of adhesive and 1 part of conductive agent, stirring and dispersing by using a high-speed centrifugal defoaming stirrer at the stirring speed of 35rpm, the dispersing speed of 3500rpm and the stirring time of 120min to obtain a conductive adhesive solution; wherein the pH value of the conductive glue solution is 9.03;
(2) dispersion of lithium iron phosphate positive electrode active material: adding an additional binder and a lithium iron phosphate positive electrode active substance into the conductive glue solution together for mixing and dispersing, wherein the stirring speed in the first step is 25rpm, the dispersing speed is 0, and the stirring time is 60 min; after scraping, the stirring speed of the second step is 40rpm, the dispersion speed is 4500rpm, and the stirring time is 120 min;
(3) defoaming: the stirring speed is-25 rpm, the dispersion speed is 0, and the stirring time is 30 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery.
Comparative example 3
The lithium iron phosphate anode slurry for the lithium ion battery in the comparative example has the following formula (the components are calculated in parts by mass):
wherein the tap density of the lithium iron phosphate is 0.93g/cm3(ii) a The pH of a 15% acrylic ester multipolymer solution was 8.92, the viscosity was 6020 mPaS; the specific surface area of SP-Li is 58m2(ii) in terms of/g. When in use, 1 part of 15 percent acrylate multipolymer solution and 3 parts of polyacrylic resin emulsion are mixed into the adhesive.
(1) Preparing a conductive glue solution: fully mixing 1 part of adhesive and 1 part of conductive agent, stirring and dispersing by using a high-speed centrifugal defoaming stirrer at the stirring speed of 35rpm, the dispersing speed of 3500rpm and the stirring time of 120min to obtain a conductive adhesive solution; wherein the pH value of the conductive glue solution is 9.03;
(2) dispersion of lithium iron phosphate positive electrode active material: adding 3 parts of binder and 95 parts of lithium iron phosphate positive active material into the conductive glue solution together for mixing and dispersing, wherein the first-step stirring speed is 25rpm, the dispersing speed is 0, and the stirring time is 60 min; after scraping, the stirring speed of the second step is 40rpm, the dispersion speed is 4500rpm, and the stirring time is 120 min;
(3) defoaming: the stirring speed is-25 rpm, the dispersion speed is 0, and the stirring time is 30 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery.
Comparative example 4
The lithium iron phosphate anode slurry for the lithium ion battery in the comparative example has the following formula (the components are calculated in parts by mass):
wherein the tap density of the lithium iron phosphate is 1.12g/cm3(ii) a The pH of a 15% acrylate multipolymer solution was 6.86, the viscosity was 2340 mPaS; the specific surface area of SP-Li is 58m2(ii) in terms of/g. When in use, 1 part of 15 percent acrylate multipolymer solution and 3 parts of polyacrylic resin emulsion are mixed into the adhesive.
The preparation method of the lithium iron phosphate anode slurry for the lithium ion battery in the comparative example comprises the following steps:
(1) preparing a conductive glue solution: fully mixing 1 part of adhesive and 1 part of conductive agent, stirring and dispersing by using a high-speed centrifugal defoaming stirrer at the stirring speed of 35rpm, the dispersing speed of 3500rpm and the stirring time of 120min to obtain a conductive adhesive solution; wherein the pH value of the conductive glue solution is 9.03;
(2) dispersion of lithium iron phosphate positive electrode active material: adding 3 parts of binder and 95 parts of lithium iron phosphate positive active material into the conductive glue solution together for mixing and dispersing, wherein the first-step stirring speed is 20rpm, the dispersing speed is 0, and the stirring time is 60 min; after scraping, the stirring speed of the second step is 45rpm, the dispersion speed is 4500rpm, and the stirring time is 120 min;
(3) defoaming: vacuum of-0.08 to-0.1 MPa, stirring speed of-20 rpm, dispersion speed of 0 and stirring time of 30 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery.
Performance testing
(1) Performance test of the positive electrode slurry (10 kg of main material), wherein fig. 1 is a schematic view of the positive electrode slurry of example 1.
Table 3 results of performance test of positive electrode slurry prepared in each example and comparative example
From the data in table 3, one can see: comparing example 2 with comparative example 1, the superiority and inferiority of the aqueous binder and the oily binder in dispersion can be obtained; when the viscosity of the (lithium iron phosphate) LFP slurry of the aqueous system is controlled in a certain range (suitable for coating), the dispersion of the slurry is better than that of an oily system (fineness difference and solid content difference), and the viscosity change can be known from 2h, and the stability of the slurry of the aqueous system is slightly better than that of the oily system; comparing example 2 with comparative example 2, it can be seen that at substitution below 0.73, the viscosity of the binder is insufficient, resulting in a significant decrease in slurry stability, with a particularly large 2h viscosity change; comparing example 2 with comparative example 3, it can be seen that at a degree of substitution above 3.0 the viscosity will be relatively high, and at a very low solids content the viscosity will remain high, and the slurry is not suitable for a coating process. Comparing example 2 with comparative example 4, it can be seen that there is a problem that the block is more likely to gel during long-term storage in the case of LFP processing having a relatively large surface.
(2) Performance test of positive pole piece
The positive electrode slurry obtained in examples 1 to 3 and comparative examples 1 to 4 was coated to form a positive electrode sheet, wherein fig. 2 shows the positive electrode sheet coated with the slurry of example 1, and a series of tests were performed:
as can be seen from the data in table 4: comparing the examples with comparative example 1, it can be found that the processing conditions of the aqueous system are better, no obvious pole piece appearance problem exists in the coating process, and a part of punctate exposed foil exists in the oily system; comparing the examples with comparative example 2, it can be understood that the pole piece adhesion is poor and the pole piece peel strength is low due to insufficient substitution; comparing the examples with comparative example 3, it can be seen that the overall peel strength of the pole piece was inferior to one grade, although there was no significant anomaly during the coating process.
TABLE 4 Performance test results of positive electrode sheets prepared in examples and comparative examples
Claims (10)
1. The lithium iron phosphate anode slurry for the lithium ion battery is characterized in that: the lithium iron phosphate anode material comprises a lithium iron phosphate anode active material, a binder and a conductive agent, and comprises the following components in parts by weight:
93-97 parts of lithium iron phosphate positive active material;
2-5 parts of a binder;
1-3 parts of a conductive agent;
wherein the specific surface area of the lithium iron phosphate positive electrode active material is 6-12 m2The adhesive contains acrylate multipolymer with the degree of substitution of 0.73-3.0.
2. The lithium iron phosphate cathode slurry for the lithium ion battery according to claim 1, wherein: the particle size distribution of the lithium iron phosphate positive active material is D10: 0-1 micron, D50: 1-2 microns, D90 not more than 5 microns, and tap density of 0.8-1.2 g/cm3。
3. The lithium iron phosphate cathode slurry for the lithium ion battery according to claim 1, wherein: the acrylic ester multipolymer accounts for 25 to 50 percent of the total mass of the adhesive.
4. The lithium iron phosphate cathode slurry for the lithium ion battery according to claim 3, wherein: the binder is a mixture of acrylate multipolymer and polyacrylic resin emulsion.
5. The lithium iron phosphate cathode slurry for the lithium ion battery according to claim 4, wherein the slurry comprises: the acrylate multipolymer is dissolved in water solution, the pH value is 6-8, and the viscosity is 1500-5000 mPa.S.
6. The lithium iron phosphate cathode slurry for the lithium ion battery according to claim 1, wherein: the specific surface area of the particles in the conductive agent is 55-65 m2/g。
7. A preparation method of lithium iron phosphate anode slurry of a lithium ion battery is characterized by comprising the following steps: the method comprises the following steps: fully mixing a conductive agent with equal mass and a binder to form a conductive glue solution, wherein the pH of the conductive glue solution is 8-11, then adding a lithium iron phosphate positive active substance and the binder, fully stirring and dispersing in the conductive glue solution, and finally defoaming and adjusting the viscosity to obtain the lithium iron phosphate positive slurry for the lithium ion battery.
8. The preparation method of lithium iron phosphate anode slurry for lithium ion batteries according to claim 7, characterized in that: the method comprises the following steps:
(1) preparing a conductive glue solution: fully stirring and dispersing the binder and the conductive agent with equal mass, wherein the stirring speed is 40-50 rpm, the dispersion speed is 4000-5000 rpm, and the stirring dispersion time is 150-210 min to obtain a conductive glue solution, wherein the pH value of the conductive glue solution is 8-11;
(2) dispersion of lithium iron phosphate positive electrode active material: adding an additional binder and a lithium iron phosphate positive electrode active substance into the conductive glue solution together, stirring and dispersing in two steps, wherein the stirring speed in the first step is 15-25 rpm, and the stirring time is 25-35 min; after scraping, the stirring speed in the second step is 25-35 rpm, the dispersion speed is 2500-3500 rpm, and the stirring time is 100-140 min;
(3) and (3) reverse defoaming: the stirring speed is-20 to-30 rpm, and the stirring time is 25 to 35 min;
(4) adjusting the viscosity: and adjusting the viscosity value of the slurry to 8000-1000 mPa.S to obtain the lithium iron phosphate anode slurry of the lithium ion battery.
9. The preparation method of lithium iron phosphate anode slurry for lithium ion batteries according to claim 8, characterized by comprising the following steps: and (4) adding deionized water to adjust the viscosity of the slurry.
10. A positive pole piece is characterized in that: the positive electrode paste is prepared by coating the positive electrode paste of any one of claims 1 to 6.
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| CN112467142A (en) * | 2020-11-25 | 2021-03-09 | 湖南高瑞电源材料有限公司 | Aqueous solution type lithium iron phosphate anode adhesive, preparation method and application thereof |
| CN113372482A (en) * | 2021-08-16 | 2021-09-10 | 江苏卓高新材料科技有限公司 | Acrylic acid multipolymer, preparation method thereof and application thereof in positive pole piece |
| CN114464791A (en) * | 2022-01-26 | 2022-05-10 | 广东羚光新材料股份有限公司 | Aqueous lithium iron phosphate anode slurry and preparation method and application thereof |
| CN114497459A (en) * | 2020-11-12 | 2022-05-13 | 荣盛盟固利新能源科技有限公司 | Lithium pre-intercalated lithium ion battery positive pole piece and lithium pre-intercalation method |
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| CN114497459A (en) * | 2020-11-12 | 2022-05-13 | 荣盛盟固利新能源科技有限公司 | Lithium pre-intercalated lithium ion battery positive pole piece and lithium pre-intercalation method |
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| CN113372482A (en) * | 2021-08-16 | 2021-09-10 | 江苏卓高新材料科技有限公司 | Acrylic acid multipolymer, preparation method thereof and application thereof in positive pole piece |
| CN114464791A (en) * | 2022-01-26 | 2022-05-10 | 广东羚光新材料股份有限公司 | Aqueous lithium iron phosphate anode slurry and preparation method and application thereof |
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| CN114551889A (en) * | 2022-04-26 | 2022-05-27 | 深圳一特科技有限公司 | Dispersing agent for lithium ion battery anode slurry and preparation method and application thereof |
| CN114899400A (en) * | 2022-05-11 | 2022-08-12 | 厦门海辰新能源科技有限公司 | Positive electrode slurry, positive electrode plate and lithium battery |
| CN114899400B (en) * | 2022-05-11 | 2023-09-08 | 厦门海辰储能科技股份有限公司 | Positive electrode slurry, positive electrode plate and lithium battery |
| CN115842101A (en) * | 2022-05-26 | 2023-03-24 | 宁德时代新能源科技股份有限公司 | Positive electrode slurry, method for producing same, positive electrode sheet, secondary battery, and electricity-using device |
| CN116805685A (en) * | 2023-08-22 | 2023-09-26 | 深圳海辰储能控制技术有限公司 | Positive electrode active material, positive electrode plate, lithium ion battery and electric equipment |
| CN116805685B (en) * | 2023-08-22 | 2024-01-23 | 深圳海辰储能控制技术有限公司 | Positive electrode active material, positive electrode plate, lithium ion battery and electric equipment |
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