阅读说明：本技术 一种用以抑制粘结剂迁移的极片干燥方法、极片和电池 (Pole piece drying method for inhibiting adhesive migration, pole piece and battery ) 是由 毛泽民 桂客 于 2020-03-27 设计创作，主要内容包括：本发明实施例涉及一种用以抑制粘结剂迁移的极片干燥方法、极片和电池。极片干燥方法包括：将涂覆有电极浆料的电极集流体放入冷冻干燥机的冷冻隔板上,在-50℃-0℃的冷冻温度下冷冻2-4小时,得到冻干极片；所述电极浆料包括电极材料、导电剂、粘接剂和溶剂；所述冷冻温度的上限根据所述溶剂的凝固点温度确定；将所述冻干极片置于露点低于-30％RH且压强为0-600Pa的干燥低压且温度维持在冷冻温度的环境中,进行一次或多次干燥处理,用以所述溶剂升华；干燥处理的总时间为5-48小时；对所述干燥处理后的冻干极片在露点低于-30％RH的环境或真空环境中进行辊压,得到所需的电极极片。(The embodiment of the invention relates to a pole piece drying method for inhibiting adhesive migration, a pole piece and a battery. The pole piece drying method comprises the following steps: putting the electrode current collector coated with the electrode slurry on a freezing partition plate of a freeze dryer, and freezing for 2-4 hours at a freezing temperature of-50-0 ℃ to obtain a freeze-dried pole piece; the electrode slurry comprises an electrode material, a conductive agent, a binder and a solvent; the upper limit of the freezing temperature is determined according to the freezing point temperature of the solvent; placing the freeze-drying pole piece in an environment with a dew point lower than-30% RH, a pressure of 0-600Pa, a drying low pressure and a freezing temperature, and carrying out one or more drying treatments for sublimation of the solvent; the total time of the drying treatment is 5 to 48 hours; and rolling the dried freeze-dried pole piece in an environment with a dew point lower than-30% RH or a vacuum environment to obtain the required electrode pole piece.)

1. A pole piece drying method for inhibiting adhesive migration is characterized by comprising the following steps:

putting the electrode current collector coated with the electrode slurry on a freezing partition plate of a freeze dryer, and freezing for 2-4 hours at a freezing temperature of-50-0 ℃ to obtain a freeze-dried pole piece; the electrode slurry comprises an electrode material, a conductive agent, a binder and a solvent; the upper limit of the freezing temperature is determined according to the freezing point temperature of the solvent;

placing the freeze-drying pole piece in an environment with a dew point lower than-30% RH, a pressure of 0-600Pa, a drying low pressure and a freezing temperature, and carrying out one or more drying treatments for sublimation of the solvent; the total time of the drying treatment is 5-48 hours;

and rolling the dried freeze-dried pole piece in an environment with a dew point lower than-30% RH or a vacuum environment to obtain the required electrode pole piece.

2. The pole piece drying method according to claim 1, wherein before the placing the electrode current collector coated with the electrode slurry on a freezing partition plate of a freeze dryer, the method further comprises:

and coating the electrode slurry on an electrode current collector in an environment with a dew point lower than-30% RH or a vacuum environment, wherein the coating thickness of the electrode slurry is 1-200 μm.

3. The pole piece drying method of claim 1, wherein the solvent is water, and the upper limit of the freezing temperature is 0 ℃.

4. The pole piece drying method of claim 1, wherein the solvent is N-methylpyrrolidone (NMP), and the upper limit of the freezing temperature is-24 ℃.

5. The pole piece drying method of claim 1, wherein the electrode material is a negative electrode material comprising one or a combination of several of nano-silicon, silica, silicon carbon, graphite, soft carbon and hard carbon;

the conductive agent comprises one or a combination of more of conductive carbon black, carbon fiber, conductive graphite and carbon nano tube;

the adhesive comprises one or more of styrene butadiene rubber, sodium carboxymethylcellulose, a polyphenolic acid binder, polyacrylonitrile and sodium alginate.

6. The method for drying the pole piece of claim 1, wherein the electrode material is a positive electrode material comprising one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel cobalt aluminate and a lithium-rich manganese-based material.

7. An electrode piece, characterized in that the electrode piece is prepared by the drying method of any one of the above claims 1-5.

8. A secondary battery comprising the electrode tab of claim 7.

9. The secondary battery according to claim 8, wherein the secondary battery is a lithium battery comprising: any one of a liquid lithium ion battery, a mixed solid-liquid metal lithium battery, an all solid-state lithium ion battery, and an all solid-state metal lithium battery.

Technical Field

The invention relates to the technical field of battery material preparation methods, in particular to a pole piece drying method for inhibiting adhesive migration, a pole piece and a battery.

Background

Due to rapid development of modern socioeconomic and science and technology, the performance of the traditional lithium ion battery can not meet the current energy requirement. The fields of rapidly developing electric automobiles, intelligent consumer electronics and the like all urgently need lithium ion batteries with higher energy density, long cycle life, low cost and high safety. In the aspect of positive and negative electrodes, the requirement on material capacity is higher and higher, and simultaneously, higher requirements on the stability and consistency of positive and negative electrode plates are also provided.

Currently, lithium ion battery electrodes are prepared by coating a mixed slurry of an active material, a conductive agent, a binder, and a solvent on a current collector. During the electrode drying process, process parameters (temperature, gas flow, pressure, heat radiation, etc.) significantly affect the microstructure of the final electrode. Traditional mode of heating evaporation to dryness mass flow body, its higher temperature can cause the adhesive to migrate the problem, and along with the drying of surface layer solvent, the inlayer solvent is gradually to the surface layer diffusion to lead to the inlayer adhesive to be along with solvent migration to being close to the surface layer side, thereby form and gather near the evaporation surface, the uneven distribution condition of exhausting near being close to the mass flow body. Uneven distribution of the binder causes a decrease in the adhesion between the electrode and the current collector, an increase in the resistance, and a decrease in the capacity.

Disclosure of Invention

The invention aims to provide a pole piece drying method, a pole piece and a battery for inhibiting the migration of a binder.

Therefore, in a first aspect, an embodiment of the present invention provides a pole piece drying method for inhibiting migration of an adhesive, where the pole piece drying method includes:

putting the electrode current collector coated with the electrode slurry on a freezing partition plate of a freeze dryer, and freezing for 2-4 hours at a freezing temperature of-50-0 ℃ to obtain a freeze-dried pole piece; the electrode slurry comprises an electrode material, a conductive agent, a binder and a solvent; the upper limit of the freezing temperature is determined according to the freezing point temperature of the solvent;

placing the freeze-drying pole piece in an environment with a dew point lower than-30% RH, a pressure of 0-600Pa, a drying low pressure and a freezing temperature, and carrying out one or more drying treatments for sublimation of the solvent; the total time of the drying treatment is 5-48 hours;

and rolling the dried freeze-dried pole piece in an environment with a dew point lower than-30% RH or a vacuum environment to obtain the required electrode pole piece.

Preferably, before the placing the electrode current collector coated with the electrode slurry on the freezing separator of the freeze dryer, the method further comprises:

and coating the electrode slurry on an electrode current collector in an environment with a dew point lower than-30% RH or a vacuum environment, wherein the coating thickness of the electrode slurry is 1-200 μm.

Preferably, the solvent is water, and the upper limit of the freezing temperature is 0 ℃.

Preferably, the solvent is N-methylpyrrolidone NMP, and the upper limit of the freezing temperature is-24 ℃.

Preferably, the electrode material is a negative electrode material and comprises one or a combination of several of nano silicon, silica, silicon carbon, graphite, soft carbon and hard carbon;

the conductive agent comprises one or a combination of more of conductive carbon black, carbon fiber, conductive graphite and carbon nano tube;

the adhesive comprises one or more of styrene butadiene rubber, sodium carboxymethylcellulose, a polyphenolic acid binder, polyacrylonitrile and sodium alginate.

Preferably, the electrode material is one of a positive electrode material including lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickel cobalt aluminate and a lithium-rich manganese-based material.

In a second aspect, an embodiment of the present invention provides an electrode sheet, where the electrode sheet is prepared by the electrode sheet drying method described in the first aspect.

In a third aspect, the embodiment of the present invention provides a secondary battery including the electrode sheet described in the second aspect.

Preferably, the secondary battery is a lithium battery including: any one of a liquid lithium ion battery, a mixed solid-liquid metal lithium battery, an all solid-state lithium ion battery, and an all solid-state metal lithium battery.

According to the pole piece drying method for inhibiting the migration of the binder, provided by the embodiment of the invention, the pole piece is frozen at the temperature of the freezing point of the solvent in the electrode slurry coated on the electrode current collector and below the freezing point, low-pressure drying treatment is carried out, the solvent is removed by sublimation, the binder of the prepared pole piece is uniformly distributed, the bonding performance of the battery electrode coating and the current collector is improved, the internal resistance of the battery electrode is reduced, and the corresponding rate capability is improved. The battery prepared by the pole piece has better cycle stability, storage life, high-temperature performance, safety performance and rate capability.

Drawings

FIG. 1 is a schematic diagram of a pole piece drying method for inhibiting adhesive migration according to an embodiment of the present invention

FIG. 2 is a graph showing a relationship between drying temperature and water content at 300Pa for 2 hours according to an embodiment of the present invention;

FIG. 3 is a graph showing the relationship between drying time and water content at-30 ℃ and 300Pa according to an example of the present invention;

FIG. 4 is a graph showing the relationship between the drying air pressure and the water content at-30 ℃ for 1 hour of drying, according to an example of the present invention;

FIG. 5 is a graph comparing the performance of electrodes prepared in example 1 of the present invention and comparative example 1 at 0.1C for 100 cycles;

fig. 6 is a graph comparing the charge and discharge performance of the electrodes prepared in example 1 of the present invention and comparative example 1 at different rates.

Detailed Description

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

The embodiment of the invention provides a pole piece drying method for inhibiting adhesive migration, which is used for preparing a battery pole piece, such as a positive pole piece or a negative pole piece of a lithium ion battery. The steps of the main method flow are shown in fig. 1, and can be executed as follows.

Step 110, putting the electrode current collector coated with the electrode slurry on a freezing partition plate of a freeze dryer, and freezing for 2-4 hours at a freezing temperature of-50-0 ℃ to obtain a freeze-dried pole piece;

specifically, the electrode slurry comprises an electrode material, a conductive agent, a binder and a solvent;

the electrode material may be a positive electrode material or a negative electrode material, and in each embodiment of the present invention, the negative electrode material is mainly illustrated.

When the electrode material is a negative electrode material, the electrode material can comprise one or a combination of several of nano silicon, silica, silicon carbon, graphite, soft carbon and hard carbon;

the conductive agent comprises one or a combination of more of conductive carbon black, carbon fiber, conductive graphite and carbon nano tube;

the adhesive comprises one or more of styrene butadiene rubber, sodium carboxymethylcellulose, a polyphenolic acid binder, polyacrylonitrile and sodium alginate.

When the electrode material is a positive electrode material, the electrode material can comprise one of nickel cobalt lithium manganate, lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickel cobalt aluminate and a lithium-rich manganese-based material.

In this step, the freezing temperature is determined according to the freezing point temperature of the solvent. For example, the freezing point temperature of the aqueous solvent material is generally 0 degrees centigrade; the freezing point temperature of-24 ℃ can be selected for the N-methylpyrrolidone (NMP) -based organic solvent material.

In this step of freezing, the freezing time is selected to ensure that the electrode slurry is thoroughly frozen.

Step 120, placing the freeze-dried pole piece in an environment with a low drying pressure of lower than-30% RH, a pressure of 0-600Pa and a freezing temperature, and performing one or more drying treatments for solvent sublimation;

specifically, the time for each drying treatment is preferably 5 to 48 hours.

In the step, the solvent is volatilized from the traditional liquid state to the gas state, and is changed into the solid state crystal which is sublimated to the gas state, the solid of the adhesive can not migrate along with the diffusion and sublimation of the solvent, and therefore the adhesive can be uniformly dispersed in the whole electrode system.

In the embodiment of the present invention, the influence of the above parameters on the content of the crystal water was respectively tested under the condition that the solvent is water at different drying temperatures, drying times and drying pressures, and the results can be respectively shown in fig. 2, fig. 3 and fig. 4.

FIG. 2 is a graph showing the relationship between drying temperature and water content under the condition of drying at 300Pa for 2 hours, and it can be seen that a better drying effect can be obtained at a temperature close to the freezing point of the solvent.

FIG. 3 is a graph showing the relationship between drying time and water content at-30 ℃ and 300Pa, and it can be seen that the crystal water content is remarkably decreased as the drying time is increased.

FIG. 4 is a graph showing the relationship between the drying air pressure and the water content under the condition of drying at-30 ℃ for 1 hour, and it can be seen that the lower the drying air pressure is, the more remarkable the decrease in the crystal water content is. And step 130, rolling the dried freeze-dried pole piece in an environment with a dew point lower than-30% RH or a vacuum environment to obtain the required electrode pole piece.

Specifically, in order to avoid the phenomenon that the pole piece is easy to expand in volume after being dried, rolling is needed. The pole piece is compacted through rolling, the volume of the pole piece is reduced, the energy density of the battery is improved, the electrode material and the conductive agent particles are contacted more tightly, the electronic conductivity is improved, the bonding strength of the coating material and the current collector is enhanced, the powder falling of the battery pole piece in the circulating process is reduced, and the circulating life and the safety performance of the battery are improved.

The electrode plate prepared by the method can be used for secondary batteries, such as any one of liquid lithium ion batteries, mixed solid-liquid metal lithium batteries, all-solid lithium ion batteries and all-solid metal lithium batteries.

The following will describe the performance and application of the pole piece drying method for inhibiting the migration of the binder and the pole piece prepared by the method in accordance with several specific examples.