CN113972373B - Preparation method of lithium iron phosphate pole piece and lithium ion battery - Google Patents

Preparation method of lithium iron phosphate pole piece and lithium ion battery Download PDF

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CN113972373B
CN113972373B CN202111172270.7A CN202111172270A CN113972373B CN 113972373 B CN113972373 B CN 113972373B CN 202111172270 A CN202111172270 A CN 202111172270A CN 113972373 B CN113972373 B CN 113972373B
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pole piece
iron phosphate
lithium iron
pore
drying
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CN113972373A (en
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苏锋
常林荣
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Zhejiang Chaoheng Power Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention relates to the technical field of lithium batteries, and discloses a preparation method of a lithium iron phosphate pole piece, aiming at the problems of porosity reduction and damaged hole integrity in the preparation method of the lithium iron phosphate pole piece, comprising the steps of adding a pore-forming agent into lithium iron phosphate active slurry and coating to obtain an initial pole piece; and (3) drying the primary pole piece, converting the primary pole piece into a semi-dried state, controlling the pore-forming agent to not form pores or to form pores in a small part, rolling, die-cutting, and heating, baking and pore-forming to obtain the lithium iron phosphate pole piece. According to the preparation method of the lithium iron phosphate pole piece, heating, drying and pore forming are carried out separately, pore forming is carried out after rolling, the semi-drying state is kept, the states of the internal and surface pores of a coating of the pole piece are effectively improved, and meanwhile, the conditions of dry cracking during pole piece coating, wrinkling during rolling, blanking of the edge of the pole piece during die cutting and the like are effectively improved.

Description

Preparation method of lithium iron phosphate pole piece and lithium ion battery
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a preparation method of a lithium iron phosphate pole piece and a lithium ion battery.
Background
The lithium iron phosphate battery has the advantages of long cycle life, high safety, low price and the like, and is widely applied to the fields of electric buses, electric passenger cars, energy storage and the like. The preparation process of the lithium iron phosphate pole piece generally comprises the following steps: mixing, coating, baking and drying, rolling and slicing, adding pore-forming agent into the mixed slurry and decomposing and pore-forming in the baking and drying process of the coating, so that the coating is provided with rich pores, and a path is provided for infiltration and absorption of electrolyte.
However, due to the thicker coating thickness and the rolling after coating, the porosity of the coating is reduced in the pole piece processing process, and meanwhile, the pores are extruded and collapsed, so that the problems of low electrolyte infiltration and absorption efficiency, low lithium ion migration rate, high internal resistance of the battery and the like are caused, and further, the battery failure performance such as poor rate performance, low discharge strength and the like are caused, and the pole piece and the battery performance are influenced. The Chinese patent application CN201811262061.X, patent name "a secondary atomization pore-forming method for lithium ion batteries", discloses that a coating is dried and pore-formed, then is sprayed in a spraying box containing pore-forming agent steam, and then is rolled and then subjected to heat treatment, so that the pore-forming agent is decomposed and pore-formed, and secondary pore-forming is formed. However, the method mainly improves the surface pores, the pores of the inner layer of the pole piece are still not improved, and the pore-forming effect is also affected during rolling. Chinese patent application CN201911061871.3, entitled "a pole piece and its preparation method and lithium ion battery", discloses that the pole piece is obtained after coating the active slurry, then cold-pressing treatment is performed under the press roller with protruding roller patterns, then pore-forming agent is coated and then heating is performed to form pores, and the method still only improves the pores on the surface layer of the pole piece.
Further, since lithium iron phosphate materials themselves have poor conductivity, in order to improve the conductivity, material manufacturers generally make the particle size of the materials small (nano-scale) and perform carbon coating. This, while improving the conductivity of the material, increases the difficulty of the processability of the material. The material has small particle size, large specific surface area and small compaction density, so that the solid content of the slurry is very low, generally only about 50 percent, in the battery manufacturing and homogenizing process, so that the pole piece is easy to dry and crack during coating, particularly the pole lug is easy to crease during high-surface-density coating and rolling, the edge of the pole piece is easy to drop during die cutting, the electrode is thicker under high-surface-density, electrolyte infiltration is difficult, an ion migration path is lengthened, polarization is increased, and the performance of the pole piece and the battery is affected.
Disclosure of Invention
Aiming at the problems of porosity reduction and damaged hole integrity of the existing preparation method of the lithium iron phosphate pole piece, the invention aims to provide the preparation method of the lithium iron phosphate pole piece, which can keep higher porosity and hole integrity of the pole piece.
Another object of the present invention is to provide a lithium iron phosphate pole piece obtained by the above method.
Another object of the present invention is to provide a lithium ion battery comprising the above lithium iron phosphate electrode sheet.
The invention provides the following technical scheme:
the preparation method of the lithium iron phosphate pole piece comprises the following steps:
(1) Adding pore-forming agent into lithium iron phosphate active slurry, uniformly dispersing, and uniformly coating on a pole piece substrate to obtain an initial pole piece;
(2) Drying and converting the primary pole piece into a semi-dry state, controlling the pore-forming agent to not form pores or to form a small part of pores, and then rolling and die-cutting to obtain the semi-dry pole piece;
(3) And heating and baking the semi-dried pole piece to form a hole to obtain the lithium iron phosphate pole piece.
According to the technical scheme, the lithium iron phosphate active slurry is coated on a base material to prepare an initial pole piece and then dried, wherein the lithium iron phosphate active slurry is conventional lithium iron phosphate positive pole slurry and comprises a lithium iron phosphate main material, a conductive agent, a binder and a solvent. The innovation of the invention is that the lithium iron phosphate anode slurry is prepared by a general and conventional formula, namely, the mass ratio of the lithium iron phosphate main material to the conductive agent to the binder is (90-96): (2-5), and the solvent dosage is equivalent to the sum of the dry powder masses obtained by the components. The addition amount of the pore-forming agent is also the conventional addition amount, namely 0.5 to 5 weight percent of the main material of the lithium iron phosphate.
When the primary sheet is dried, the drying conditions are controlled so that the slurry is converted into a semi-dry state, and the pore-forming agent is kept to perform no pore-forming or less pore-forming, but the pore-forming is carried out after rolling, so that the pore-forming cannot be blocked, closed and destroyed during rolling, and the pore-forming after rolling synchronously improves the pores in the coating and the pores in the surface layer, thereby improving the porosity and the pore integrity of the pole piece. Meanwhile, the primary sheet is converted into a semi-dry pole piece in a semi-dry state, so that the surface of the pole piece can be kept free of dry cracking, folds are avoided during rolling, and material dropping is avoided during die cutting. In the prior art, the technician has the thinking inertia of completely drying the primary pole piece when preparing the lithium iron phosphate pole piece, and can not think about the conversion into a semi-dry state in the application. This is because the rolling and subsequent operations require the pole pieces to be heat dried and dehumidified. Generally, high drying is advantageous for twin-roll pressing, and sticking to the rolls can be avoided, so drying is selected. And the high temperature in the drying process brings pore-forming of pore-forming agent, so that the drying is not only favorable for dehumidification, but also can synchronously perform pore-forming, thereby greatly reducing the production cost, shortening the drying time and improving the production efficiency. Meanwhile, the main factors of pole piece surface dry cracking, die cutting and material dropping and the like are the properties of the slurry (small particle size, large specific surface area, small compaction density and the like), and the technician does not notice the effect of converting the primary piece into a semi-dry state, which is beneficial to the improvement of pole piece surface dry cracking and the like.
As a preferable mode of the method, the drying mode in the step (2) is heating and drying, and the heating and drying temperature is less than or equal to the pore-forming temperature of the pore-forming agent. The heating and drying are convenient to realize, and the difficulty in realizing the economy and technology is low. The heating and drying temperature is kept not to exceed the pore-forming temperature of the pore-forming agent, so that the pore-forming agent does not form pores at all or forms pores at least partially. The inventor researches find that the effect of small part of pore forming on the performance of the pole piece is superior to that of completely non-pore forming, mainly because the surface compaction of the semi-dried pole piece after rolling is performed, if the pore forming is not performed at all, the pore forming agent needs to break through compaction pressure brought by rolling to form pores after rolling, the process is relatively intense, the surface morphology of the coating and the pore structure are changed, and if part of pore forming is performed, partial pore forming, especially pore paths of inner pores, still exist (although the integrity is reduced), space is provided for the pore forming after rolling, and the pressure of partial gas escape is released, so that the subsequent pore forming is more mild, and the pore and the morphology of the coating are maintained.
Preferably, the pore-forming agent is one or more of ammonium bicarbonate, ammonium carbonate and ammonium chloride. The ammonium bicarbonate, ammonium carbonate and ammonium chloride have proper decomposition temperature, are not too high nor particularly low, and are favorable for realizing the semi-dry state, wherein the ammonium bicarbonate is partially decomposed at 60-80 ℃ to generate CO 2 And ammonia carbonate, which is largely converted into ammonia and CO at higher temperatures 2 The decomposition temperature of ammonia carbonate is generally above 90℃and that of ammonium chloride is 100 ℃. At the same time, the actual temperature in the coating will be significantly lower than the operating temperature, taking into account the heat absorption of the coating slurry itself and the volatilization of the solvent, even at 70 ℃, there is only a small degree of pore formation for the ammonia bicarbonate, so that no or a small portion of pore formation is maintained. Meanwhile, lower pore-forming temperature requires lower heating and drying temperature, and the heating and drying time is prolonged, so that the efficiency is reduced.
Preferably, the heat drying temperature is 40 to 85 ℃.
Preferably, the heating and drying are gradient temperature variable drying, and the heating and drying temperatures are as follows: 60+ -10 ℃, 65+ -10 ℃, 70+ -10 ℃, 65+ -10 ℃. The temperature for starting drying is not excessively high, so that the solvent is not evaporated strongly, and the gradient is not excessively high, so that the drying crack is not caused, and a more moderate drying effect can be achieved through the preferable gradient temperature-variable drying, so that the basic shape of the coating is maintained.
Preferably, the semi-dried state is a dryness of 50 to 90%.
Preferably, the semi-dried state is a dryness of 60 to 80%.
The dryness refers to the mass ratio of the pole piece after baking and pore forming in the step (3) to the semi-dry pole piece obtained in the step (2), namely the mass ratio after treatment and before treatment in the step (3). The larger the dryness is, the closer the quality of the pole piece baked in the step (3) is to the quality of the semi-dried pole piece obtained in the step (2), which means that the baking in the step (3) has no solvent which can be evaporated, a large amount of solvent is evaporated in the step (2), and the drying degree of the step (2) is deep; the small dryness means that the mass of the pole piece baked in the step (3) is greatly different from that of the semi-dried pole piece obtained in the step (2), which indicates that a large amount of solvent is evaporated in the step (3), while the amount of the solvent evaporated in the step (2) is small, and the dryness of the step (2) is shallow. Therefore, the greater the dryness, the deeper the dryness of step (2), the lesser the dryness, the shallower the dryness in step (2).
Preferably, the heating and baking are vacuum heating and baking.
As a preferred embodiment of the method of the present invention, the vacuum heating baking process is as follows: preheating the semi-dry pole piece for 15-30 min at 80-110 ℃ and vacuum pressure of less than or equal to 200 Pa; then inert gas is introduced to boost the pressure to 50000 Pa-80000 Pa, the vacuum pressure is kept for 40-60 min, and then the vacuum pressure is reduced to be less than or equal to 50Pa and kept for 200-300 min. Because the step (2) is in a semi-dry state, the coating still contains the solvent, and the pore-forming agent does not obviously form pores, the volatilization of the residual solvent and the pore-forming of the pore-forming agent are realized through vacuum heating and drying.
A lithium ion battery comprising the lithium iron phosphate pole piece obtained by the preparation method. The performance of the lithium iron phosphate pole piece is improved and the performance of the lithium ion battery is also improved due to the improvement of the pore-forming condition.
The beneficial effects of the invention are as follows:
according to the preparation method of the lithium iron phosphate pole piece, heating, drying and pore forming are carried out separately, pore forming is carried out after rolling, the semi-drying state is kept, the internal and surface pore states of a coating of the pole piece are effectively improved, and meanwhile, the conditions of dry cracking during pole piece coating, wrinkling during rolling, material dropping at the edge of the pole piece during die cutting and the like are effectively improved.
Drawings
Fig. 1 is a topography of a lithium iron phosphate pole piece prepared in example 1.
Fig. 2 is a topography of a lithium iron phosphate pole piece prepared in example 8.
Detailed Description
The following is a further description of embodiments of the invention.
Unless otherwise indicated, all starting materials used in the present invention are commercially available or are commonly used in the art, and unless otherwise indicated, the methods in the examples below are all conventional in the art.
To maintain consistency, the lithium iron phosphate active slurries in the following examples and comparative examples consist of the following components in mass ratio: lithium iron phosphate, PVDF, conductive carbon black, solvent nmp=93:2:3:93.
The substrates used were all aluminum foils 15 μm thick.
Example 1
The preparation method of the lithium iron phosphate pole piece comprises the following steps:
(1) Adding pore-forming agent ammonium bicarbonate NH into lithium iron phosphate active slurry 4 HCO 3 ，NH 4 HCO 3 The addition amount is 1 weight percent of the dosage of the lithium iron phosphate, then the mixed slurry is obtained by stirring uniformly by a stirrer, and then the slurry is coated on an aluminum foil with the thickness of 15 mu m, and the double-sided density is 480g/m 2 Obtaining a primary pole piece;
(2) The length of four sections of baking ovens of the coating machine is 12m, the running speed of the coating machine is adjusted to be 5m/min, and the air quantity of the baking ovens is 500m 3 And (3) the first section to the fourth section of the temperature of the oven are respectively: 60 ℃, 65 ℃, 70 ℃ and 65 ℃ to obtain a pole roll with the dryness of 70 percent, and then rolling and die-cutting by conventional pressure to obtain a semi-dry pole piece;
(3) The semi-dry pole piece is sent into a vacuum oven, the vacuum oven is preheated for 30min at 110 ℃ under the vacuum pressure of 200Pa, then nitrogen is introduced to boost the pressure to 80000Pa and the vacuum pressure is kept for 40min, then the vacuum pressure is reduced to 50Pa and the vacuum pressure is kept for 200min, and the lithium iron phosphate pole piece is obtained, and as shown in figure 1, the surface is smooth and no material dropping phenomenon exists.
Example 2
The difference from example 1 is that:
in the step (2), the running speed of the coating machine is 6m/min, and the temperatures of the first section to the fourth section of the oven are respectively: 62 ℃, 68 ℃, 75 ℃ and 65 ℃ to obtain a pole roll with the dryness of 70 percent;
in the step (3), the vacuum oven is preheated for 15min at 90 ℃ under the vacuum pressure of 100Pa, then nitrogen is introduced to boost the pressure to 50000Pa, the vacuum pressure is kept for 60min, and then the vacuum pressure is reduced to 40Pa and kept for 300min.
Example 3
The difference from example 1 is that:
in the step (2), the running speed of the coating machine is 6m/min, and the temperatures of the first section to the fourth section of the oven are respectively: 65 ℃, 70 ℃, 75 ℃ and 70 ℃ to obtain a pole coil with a dryness of 75%;
in the step (3), the vacuum oven is preheated for 30min at 110 ℃ under the vacuum pressure of 200Pa, then nitrogen is introduced to raise the pressure to 80000Pa, the vacuum pressure is kept for 60min, and then the vacuum pressure is lowered to 50Pa and kept for 300min.
Example 4
The difference from example 1 is that:
in the step (2), the running speed of the coating machine is regulated to be 6m/min, and the temperatures of the first section to the fourth section of the oven are respectively as follows: 65 ℃, 70 ℃, 80 ℃ and 70 ℃ to obtain a pole coil with the dryness of 80 percent;
in the step (3), the vacuum oven is preheated for 30min at 110 ℃ under the vacuum pressure of 200Pa, then nitrogen is introduced to raise the pressure to 80000Pa, the vacuum pressure is kept for 50min, and then the vacuum pressure is lowered to 50Pa and kept for 220min.
Example 5
The difference from example 1 is that:
in the step (2), the running speed of the coating machine is adjusted to 7m/min, and the temperatures of the first section to the fourth section of the oven are respectively: 75 ℃, 80 ℃, 85 ℃ and 75 ℃ to obtain a pole coil with the dryness of 85 percent;
in the step (3), the vacuum oven is preheated for 30min at 110 ℃ under the vacuum pressure of 200Pa, then nitrogen is introduced to raise the pressure to 80000Pa, the vacuum pressure is kept for 55min, and then the vacuum pressure is lowered to 50Pa and kept for 270min.
Example 6
The difference from example 1 is that the drying and removal are carried out in step (3) by heating, the temperature of the oven is 110 ℃, and the drying time is 270 minutes.
Example 7
The difference from example 1 is that the pore-forming agent used is an equivalent amount of ammonium chloride.
Example 8
The difference from example 7 is that isothermal drying is adopted in the step (2), namely the length of four sections of baking oven of the coating machine is 12m, the running speed of the coating machine is adjusted to 5m/min, and the air quantity of the baking oven is 500m 3 /h, but the drying temperature was maintained at 80 ℃.
The obtained lithium iron phosphate pole piece is shown in figure 2, and the leftover is subject to material dropping.
Comparative example 1
The difference from example 1 is that the oven temperatures in step (2) are respectively: 85 ℃, 90 ℃, 95 ℃, 85 ℃ and 95% of the dryness of the pole rolls.
Comparative example 2
The difference from example 1 is that the oven temperatures in step (2) are respectively: 90 ℃, 95 ℃, 100 ℃, 90 ℃ and 98% of the dryness of the pole rolls.
Comparative example 3
The difference from example 1 is that the oven temperatures in step (2) are respectively: 95 ℃, 100 ℃, 105 ℃, 95 ℃ and 98% of the dryness of the pole rolls.
Comparative example 4
The difference from example 1 is that the oven temperatures in step (2) are respectively: 95 ℃, 100 ℃, 105 ℃, 95 ℃ and 80% of the dryness of the pole rolls.
Comparative example 5
And (3) adopting a conventional preparation process of the lithium iron phosphate pole piece, namely, compared with the embodiment 1, drying the initial pole piece obtained in the step (1) at 100 ℃, and then rolling and die-cutting to obtain the lithium iron phosphate pole piece.
Performance testing
The morphology and electrical properties of the lithium phosphate pole pieces obtained in each example and comparative example are shown in table 1 below.
The dryness is the percentage of the mass of the pole piece processed in the step (3) to the mass of the semi-dried pole piece processed in the step (2).
Porosity was measured using a mercury porosimeter.
The electrical property test is to assemble the lithium iron phosphate positive plate obtained in each example or comparative example into a lithium iron phosphate battery, test the self discharge rate, the rate discharge capacity retention rate and the cycle property of the battery, and assemble the battery as follows:
(1) Preparing a negative electrode sheet: artificial graphite: conductive carbon black SP: dispersant CMC: binder SBR, according to mass ratio 93:2:2:3, dispersing, uniformly coating on the copper foil, oven drying, and rolling to prepare a pole piece;
(2) The prepared positive and negative electrode plates are placed on two sides of a diaphragm to be coiled, electrode lugs are welded, packaged, injected with liquid, formed, pumped, sealed and separated to prepare a lithium iron phosphate battery, the diaphragm is a PP film, and the lithium salt concentration of the electrolyte is LiPF of 1mol/L 6 The solvent ratio is 55% EMC+35% EC+10% PC, and the additive is 2% VC and 1% PS.
Self-discharge rate = C2/C1: fully charging the battery core with the capacity of C1, and discharging after standing at 25 ℃ for 28 days, wherein the discharge capacity is C2;
cycle performance: in the environment of 25 ℃, the first step is as follows: constant voltage and cut-off current are respectively carried out after the constant current of 0.5C is charged to 3.65V and 0.05C; and a second step of: standing for 10 minutes; and a third step of: constant-current discharge of 1.0C to 2.5V, and fourth step: standing for 10 minutes; fifth step: and cycling the first step to the fourth step until the battery capacity retention rate is less than 80%.
Rate discharge capacity retention rate = last discharge capacity/first discharge capacity.
TABLE 1 morphology and electrical Properties of lithium phosphate Pole pieces
Figure BDA0003293817950000071
Remarks: the dry state in comparative example 5 was such that the primary sheet was dried at 100 c until the solvent was substantially completely removed, with completion of pore-forming.
From the above table, it can be seen that the edge of the pole piece is dropped to cause higher self-discharge rate of the battery, the larger porosity is favorable for high-rate discharge of the battery and improvement of electrolyte absorption capacity, but the porosity is high and does not represent that the electrical property is certain to be high, the microstructure integrity of the hole can ensure that the pole piece keeps stable structure in the circulation process, the circulation is facilitated, meanwhile, the electrolyte retention amount is higher, and the electrolyte required by long circulation can be maintained, and the method specifically comprises the following steps:
as can be seen from the comparison of examples 1 to 5 and comparative examples 1 to 3 and comparative example 5, controlling the appropriate dryness and drying temperature will facilitate the pore structure of the pole piece, avoid phenomena such as material dropping and dry cracking, and improve the electrical properties;
example 6 compared with example 1, the high temperature of 110 ℃ is adopted for baking and pore forming all the time, and the solvent evaporation amount is small due to quick drying, but a large amount of pore forming is carried out, so that the pore forming power of the step (3) is insufficient, and the porosity and the electrical property are reduced compared with example 1. In the embodiment 7, compared with the embodiment 1, ammonium chloride is adopted as a pore-forming agent, the temperature is low, so that the pore-forming is not performed in the step (2), the pore-forming is performed in the step 3, the pore-forming is more intense, the porosity of the pole piece is equal to that of the embodiment 1, but the pore structure is poor, and therefore, the electrical property of the pole piece is reduced compared with that of the embodiment 1;
in the embodiment 8, compared with the embodiment 1, ammonium chloride is adopted as a pore-forming agent, but in the step (2), the constant temperature 80 is adopted for drying, the solvent is evaporated vigorously, the dryness and the porosity are equivalent to those of the embodiment 1, but the pore structure is poor, a slight blanking phenomenon exists in the die cutting process, and the electrical property of the pole piece is reduced compared with that of the embodiment 1;
comparative example 4 compared to example 1, a higher drying temperature (above the decomposition temperature of ammonium bicarbonate) was used in step (2) and run faster to maintain the same semi-dry state, so that no material was lost, cracking was occurred, but most of the ammonium bicarbonate was porous, so that the pore-forming power in step (3) was insufficient, and the pore-forming in step (2) was also broken by rolling, so that the porosity and pore structure were reduced, and the electrical properties were also reduced.

Claims (9)

1. The preparation method of the lithium iron phosphate pole piece is characterized by comprising the following steps of:
(1) Adding pore-forming agent into lithium iron phosphate active slurry, uniformly dispersing, and uniformly coating on a pole piece substrate to obtain an initial pole piece;
(2) Drying the primary pole piece, converting into a semi-dry state, controlling a small part of pore-forming agent to form pores, and then rolling and die-cutting to obtain the semi-dry pole piece;
(3) Heating and baking the semi-dried pole piece to form a hole to obtain a lithium iron phosphate pole piece;
the semi-dry state is a dryness of 50 to 90%.
2. The method for preparing a lithium iron phosphate pole piece according to claim 1, wherein the drying mode in the step (2) is heating and drying, and the heating and drying temperature is the pore-forming temperature of the pore-forming agent.
3. The method for preparing a lithium iron phosphate pole piece according to claim 2, wherein the pore-forming agent is one or more of ammonium bicarbonate, ammonium carbonate and ammonium chloride.
4. The method for preparing a lithium iron phosphate pole piece according to claim 3, wherein the heating and drying temperature is 40-85 ℃.
5. The method for preparing the lithium iron phosphate pole piece according to claim 3, wherein the heating and drying are gradient temperature variable drying, and the heating and drying temperatures are as follows: 60+ -10 ℃, 65+ -10 ℃, 70+ -10 ℃, 65+ -10 ℃.
6. The method for preparing a lithium iron phosphate sheet according to claim 1, wherein the semi-dried state is a dryness of 60 to 80%.
7. The method for preparing a lithium iron phosphate electrode sheet according to claim 1, wherein the heating and baking is vacuum heating and baking.
8. The method for preparing the lithium iron phosphate pole piece according to claim 7, wherein the vacuum heating and baking process is as follows: preheating the wet pole piece for 15-30 min at 80-110 ℃ and vacuum pressure of less than or equal to 200 Pa; then inert gas is introduced to boost the pressure to 50000 Pa-80000 Pa, the vacuum pressure is kept for 40-60 min, and then the vacuum pressure is reduced to be less than or equal to 50Pa and kept for 200-300 min.
9. A lithium ion battery comprising a lithium iron phosphate pole piece obtained by the production method according to any one of claims 1 to 8.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102157267A (en) * 2011-04-02 2011-08-17 中山大学 Scale manufacturing method of super capacitor electrode
CN111725479A (en) * 2020-07-16 2020-09-29 深圳市信宇人科技股份有限公司 Lithium ion battery pole piece and preparation method thereof

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* Cited by examiner, † Cited by third party
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KR100682862B1 (en) * 2005-01-11 2007-02-15 삼성에스디아이 주식회사 Electrode for electrochemical cell, manufacturing method thereof, and electrochemical cell containing the electrode
CN102655229B (en) * 2012-03-19 2014-11-05 宁德新能源科技有限公司 Pore-forming method for diaphragms of lithium ion batteries
CN108258323B (en) * 2018-01-30 2019-09-10 陕西煤业化工技术研究院有限责任公司 A kind of production method of high specific energy solid lithium battery
CN110911630A (en) * 2019-10-23 2020-03-24 东北大学 High-porosity lithium ion battery pole piece and preparation method thereof
CN112420987B (en) * 2020-11-26 2022-06-14 惠州亿纬锂能股份有限公司 High-porosity lithium ion battery pole piece and preparation method and application thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102157267A (en) * 2011-04-02 2011-08-17 中山大学 Scale manufacturing method of super capacitor electrode
CN111725479A (en) * 2020-07-16 2020-09-29 深圳市信宇人科技股份有限公司 Lithium ion battery pole piece and preparation method thereof

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