阅读说明：本技术 一种电极极片、及其制备方法和用途 (Electrode pole piece, and preparation method and application thereof ) 是由 陈仕谋 王如梦 王晓阳 刘玉文 张锁江 于 2019-10-25 设计创作，主要内容包括：本发明涉及一种电极极片的制备方法,所述方法包括如下步骤：(1)将多巴胺溶解在缓冲溶液中,再加入氧化剂,得到反应体系；(2)将反应极片浸润到反应体系中,得到电极极片。本发明在电极极片上引入多巴胺上的多功能基团,在充放电过程中,附着在极片表面的多电子胺基可以促进电解液中电解质和添加剂的还原,促使电极表面形成一层稳定的SEI膜,一方面可以尽快将电解液与电极阻隔开来,减少接触；另一方面则可以防止溶剂分子的共嵌入,两个方面均可以减轻对电极材料结构的破坏,从而降低不可逆容量的产生,进而提高电极的循环性能,并减小了充放电过程中体积膨胀带来的电极片破裂粉碎。(The invention relates to a preparation method of an electrode plate, which comprises the following steps: (1) dissolving dopamine in a buffer solution, and adding an oxidant to obtain a reaction system; (2) and infiltrating the reaction pole piece into a reaction system to obtain the electrode pole piece. In the invention, a multifunctional group on dopamine is introduced on an electrode plate, and in the charging and discharging processes, the multi-electron amino attached to the surface of the electrode plate can promote the reduction of electrolyte and additives in electrolyte and promote the formation of a stable SEI film on the surface of the electrode, so that the electrolyte and the electrode can be separated as soon as possible to reduce contact; on the other hand, the co-embedding of solvent molecules can be prevented, and the damage to the electrode material structure can be reduced on both aspects, so that the generation of irreversible capacity is reduced, the cycle performance of the electrode is further improved, and the breakage and crushing of the electrode sheet caused by volume expansion in the charging and discharging processes are reduced.)

1. A preparation method of an electrode plate is characterized by comprising the following steps:

(1) dissolving dopamine in a buffer solution, and adding an oxidant to obtain a reaction system;

(2) and infiltrating the reaction pole piece into a reaction system to obtain the electrode pole piece.

2. The method according to claim 1, wherein the buffer solution of step (1) is prepared by a process comprising: dissolving a surfactant in water, and then adding acid to adjust the pH value to obtain a buffer solution;

preferably, the surfactant is tris;

preferably, the acid is hydrochloric acid;

preferably, the pH value of the buffer solution is 5-10, preferably 7-9.

3. The method according to claim 1 or 2, wherein the oxidant in step (1) comprises any one or a combination of at least two of oxygen, air, ammonium persulfate, hydrogen peroxide and ferric chloride, preferably ammonium persulfate;

preferably, the concentration of dopamine in the reaction system is 1-5 g/L;

preferably, the concentration of the oxidant in the reaction system is 10-30 mmol/L;

preferably, the concentration of the surfactant in the reaction system is 5-15 mmol/L.

4. The preparation method according to any one of claims 1 to 3, wherein the time for soaking the reaction pole piece in the step (2) into the reaction system is 0.1 to 2 hours, preferably 0.1 to 1 hour;

preferably, the temperature of the reaction system in the step (2) is 30-60 ℃.

5. The method according to any one of claims 1 to 4, wherein the reaction electrode sheet of step (2) comprises a positive electrode sheet or a negative electrode sheet;

preferably, the negative pole piece is a silicon-carbon negative pole piece;

preferably, the preparation process of the silicon-carbon negative electrode plate comprises the following steps: grinding and mixing a silicon-carbon negative electrode material, a water-based binder and a conductive agent, adding a solvent, stirring to obtain an electrode slurry, coating the electrode slurry on a current collector, and drying to obtain a silicon-carbon negative electrode piece;

preferably, the mass ratio of the silicon-carbon negative electrode material to the aqueous binder to the conductive agent is 3-16: 1: 1;

preferably, the stirring time is 5-10 h;

preferably, the solvent is water;

preferably, the drying is vacuum drying, the drying temperature is 60-90 ℃, and the drying time is 8-10 hours;

preferably, the current collector is a copper foil;

preferably, the silicon carbon negative electrode material comprises silicon carbon 650 and/or silicon carbon 480;

preferably, the conductive agent is super P.

6. The preparation method according to one of claims 1 to 5, wherein the step (2) further comprises a post-treatment process after the reaction pole piece is soaked into the reaction system;

preferably, the post-treatment is vacuum drying;

preferably, the drying temperature is 60-90 ℃ and the drying time is 8-10 h.

7. The method of any one of claims 1 to 6, wherein the method comprises the steps of:

(1) grinding and mixing a silicon-carbon negative electrode material, a water-based binder and a conductive agent, wherein the mass ratio of the silicon-carbon negative electrode material to the water-based binder to the conductive agent is 3-16: 1:1, adding water, stirring for 5-10 h to obtain an electrode slurry, coating the electrode slurry on a current collector, and performing vacuum drying at 60-90 ℃ for 8-10 h to obtain a silicon-carbon negative electrode piece;

(2) dissolving trihydroxymethyl aminomethane in water, and then adding acid to adjust the pH value to 7-9 to obtain a buffer solution;

(3) dissolving dopamine in a buffer solution, and adding an oxidant to obtain a reaction system, wherein the concentration of the dopamine in the reaction system is 1-5 g/L, the concentration of the oxidant is 10-30 mmol/L, and the concentration of tris (hydroxymethyl) aminomethane is 5-15 mmol/L;

(4) and infiltrating the silicon-carbon negative electrode plate into a reaction system for 0.1-1 h, wherein the temperature of the reaction system is 30-60 ℃, and vacuum drying is carried out for 8-10 h at the temperature of 60-90 ℃ to obtain the electrode plate.

8. An electrode piece, characterized in that the electrode piece is prepared by the method of any one of claims 1 to 7.

9. The electrode piece according to claim 8, wherein the electrode piece comprises a current collector and an active material layer and a polydopamine material layer which are sequentially arranged on the surface of the current collector;

preferably, the polydopamine material layer comprises any one or a combination of at least two of dopamine monomer, dihydroxyindole, indole dione and catechol derivative and polymer thereof.

10. Use of an electrode sheet according to claim 8 or 9 in any one or a combination of at least two of a lithium ion battery, a sodium ion battery and a potassium ion battery.

Technical Field

The invention belongs to the technical field of batteries, and particularly relates to an electrode plate, and a preparation method and application thereof.

Background

With the large consumption of fossil fuels, environmental problems are becoming more severe, and the development of new energy sources to replace traditional fossil fuels is at a premium. Lithium Ion Batteries (LIBs) have been widely used in portable electronic devices (e.g., mobile phones, notebook computers, and cameras), but with the development of Electric Vehicles (EVs) and Energy Storage Systems (ESS), the demand for the capacity and performance of the battery is higher and higher, and the development of high-energy, environmentally-friendly, green power sources is also urgent.

The silicon has ultrahigh theoretical intercalation capacity which is about 4200mAh/g, which is more than ten times of the limit specific capacity of the current commercial graphite negative electrode, and the potential difference between the silicon and the silicon is only 0.2V and is lower than that of most alloy and metal oxide negative electrode materials. The silicon-based negative electrode has high energy density due to low working voltage and high specific capacity, and is considered as the negative electrode material of the lithium ion battery with the most development potential. However, during intercalation and deintercalation, silicon can generate serious volume change (> 300%), which causes material pulverization, active substances lose electric contact with a current collector and a conductive agent, so that capacity is rapidly attenuated, and the cycle life of the silicon surface is severely limited by an unstable Solid Electrolyte Interface (SEI) film.

At present, a plurality of solutions are provided for solving the problems of the silicon negative electrode, including compounding with a carbon material, using a novel binder, adopting an electrolyte additive and the like, although a series of disadvantages caused by volume expansion are reduced to a certain extent, the inherent disadvantages of the silicon negative electrode are not fundamentally solved. Therefore, there is a need to continue to enhance the investigation of silicon anodes.

CN109671941A discloses a silicon-carbon negative electrode material and a preparation method thereof, which comprises the following steps from inside to outside: silicon/silicon oxide particles, an N-3- (trimethoxysilyl) propyl vinyl diamine molecular layer, a carbon nanotube conducting layer and a polydopamine carbonization layer, wherein the silicon/silicon oxide particles are silicon or a multivalent oxide of silicon or a mixture of the silicon or the multivalent oxide of silicon, and the thickness of the N-3- (trimethoxysilyl) propyl vinyl diamine molecular layer is 1-10 mu m; in the polydopamine carbon layer, polydopamine macromolecules uniformly form a film on the outermost layer to coat silicon/silicon oxide particles and carbon nanotubes, and the thickness of the film is 0.01-3 mu m. However, the charge and discharge performance of the silicon-carbon negative electrode material is sharply reduced at a large rate.

CN109065848A discloses a silicon-carbon composite electrode material with a hollow structure and a preparation method thereof, wherein the preparation method comprises the following steps: s1: dispersing the nano silicon particles into an organic solvent, adding a coupling agent, adjusting the pH value to 3-4, washing and drying to obtain modified nano silicon particles; s2: respectively preparing a water phase solution and an oil phase solution, dispersing the modified nano silicon particles obtained in the step S1 into the oil phase solution, adding the dispersed modified nano silicon particles into the water phase solution, adding an initiator, centrifuging, washing and drying to obtain a composite material of a layer of polymer coated on the nano silicon particles; s3: adding the composite material obtained in the step S2 into a Tris buffer solution, adding dopamine hydrochloride, and performing centrifugation, filtration and drying to obtain a composite material of a double-layer polymer coated on the nano silicon particles; s4: and carbonizing the composite material obtained in the step S3 to obtain the silicon-carbon composite electrode material. However, the silicon carbon negative electrode material has poor long cycle performance, and the structure thereof is damaged by repeated charge and discharge.

Therefore, a need exists in the art for a novel electrode sheet preparation method, which has the advantages of simple preparation process and strong repeatability, improves the stability of cycle performance on the basis of not reducing the electrode capacity, and reduces the problems of electrode sheet breakage, crushing and the like caused by volume expansion in the charging and discharging processes.

Disclosure of Invention

In view of the defects of the prior art, one of the objectives of the present invention is to provide an electrode sheet, a method for preparing the same, and a use of the same. The electrode plate provided by the invention has the advantages of simple preparation process and strong repeatability, improves the stability of the cycle performance on the basis of not reducing the electrode capacity, and reduces the problems of electrode plate breakage, crushing and the like caused by volume expansion in the charging and discharging processes.

In order to achieve the purpose, the invention adopts the following technical scheme:

one of the purposes of the invention is to provide a preparation method of an electrode plate, which comprises the following steps:

(1) dissolving dopamine in a buffer solution, and adding an oxidant to obtain a reaction system;

(2) and infiltrating the reaction pole piece into a reaction system to obtain the electrode pole piece.

Dissolving dopamine in a buffer solution, adding an oxidant to accelerate the speed of polymerization reaction, then infiltrating a reaction pole piece into a reaction system, oxidizing an o-catechol group of dopamine hydrochloride into o-diphenoquinone in a weak alkaline buffer solution, then carrying out 1, 4-Michael addition and intramolecular cyclization, and forming a polydopamine layer after a series of oxidative rearrangement.

In the invention, a multifunctional group on dopamine is introduced on an electrode plate, and in the charging and discharging processes, the multi-electron amino attached to the surface of the electrode plate can promote the reduction of electrolyte and additives in electrolyte and promote the formation of a stable SEI film on the surface of the electrode, so that the electrolyte and the electrode can be separated as soon as possible to reduce contact; on the other hand, the co-embedding of solvent molecules can be prevented, and the damage to the electrode material structure can be reduced on both aspects, so that the generation of irreversible capacity is reduced, the cycle performance of the electrode is further improved, and the breakage and crushing of the electrode sheet caused by volume expansion in the charging and discharging processes are reduced.

Preferably, the preparation process of the buffer solution in step (1) comprises: the surfactant is dissolved in water, and then acid is added to adjust the pH value, so as to obtain a buffer solution.

Preferably, the surfactant is tris.

Preferably, the acid is hydrochloric acid.

Preferably, the pH value of the buffer solution is 5-10, preferably 7-9, such as 5, 6, 7, 8 or 9.

Preferably, the oxidant in step (1) comprises any one or a combination of at least two of oxygen, air, ammonium persulfate, hydrogen peroxide and ferric chloride, preferably ammonium persulfate.

The oxidizing agent of the present invention acts to accelerate the reaction rate of oxidative polymerization.

Preferably, the concentration of dopamine in the reaction system is 1-5 g/L, such as 1.2g/L, 1.5g/L, 1.8g/L, 2g/L, 2.5g/L, 3g/L, 3.5g/L, 4g/L or 4.5 g/L.

The concentration of dopamine in the reaction system is too high, so that the reaction is not accelerated, and the polymerization process is possibly hindered; too small a concentration may not be sufficient to produce the desired amount of polydopamine.

Preferably, the concentration of the oxidant in the reaction system is 10-30 mmol/L, such as 12mmol/L, 15mmol/L, 18mmol/L, 20mmol/L, 22mmol/L, 25mmol/L, 26mmol/L or 28 mmol/L.

The concentration of the oxidant in the reaction system is too high, other side reactions can be caused, and the reaction speed is not easy to control; the concentration is too low to accelerate the reaction.

Preferably, the concentration of the surfactant in the reaction system is 5-15 mmol/L, such as 5mmol/L, 5.5mmol/L, 6mmol/L, 7mmol/L, 8mmol/L, 9mmol/L, 10mmol/L, 11mmol/L, 12mmol/L, 13mmol/L or 14 mmol/L.

Excessive concentration of the surfactant in the reaction system can introduce excessive impurities into the polymer; too little concentration is not sufficient to achieve an optimal pH.

Preferably, the time for soaking the reaction electrode sheet in the step (2) into the reaction system is 0.1-2 hours, preferably 0.1-1 hour, and further preferably 40min, such as 0.2 hour, 0.4 hour, 0.5 hour, 0.6 hour, 0.8 hour, 1 hour, 1.2 hour, 1.5 hour, or 1.8 hour.

The time for soaking the reaction pole piece into the reaction system (self-polymerization reaction time) is less than 0.1h, which is not enough to form a poly-dopamine layer on the surface of the pole piece; the time is longer than 2h, the formed polydopamine layer is too thick, and the impedance of the interface is increased.

Preferably, the temperature of the reaction system in the step (2) is 30 to 60 ℃, for example, 32 ℃, 35 ℃, 38 ℃, 40 ℃, 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃ or 58 ℃.

Preferably, the reaction pole piece in the step (2) comprises a positive pole piece or a negative pole piece.

Preferably, the negative electrode plate is a silicon-carbon negative electrode plate.

Preferably, the preparation process of the silicon-carbon negative electrode plate comprises the following steps: grinding and mixing the silicon-carbon negative electrode material, the water-based binder and the conductive agent, adding the solvent, stirring to obtain electrode slurry, coating the electrode slurry on a current collector, and drying to obtain the silicon-carbon negative electrode piece.

Preferably, the mass ratio of the silicon-carbon negative electrode material, the aqueous binder and the conductive agent is 3-16: 1:1, for example, 4:1:1, 5:1:1, 6:1:1, 7:1:1, 8:1:1, 9:1:1, 10:1:1, 11:1:1, 12:1:1, 13:1:1, 14:1:1, or 15:1: 1.

Preferably, the stirring time is 5-10 h, such as 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h or 9.5 h.

Preferably, the solvent is water.

Preferably, the drying is vacuum drying, the drying temperature is 60-90 ℃, and the drying time is 8-10 hours; the drying temperature is, for example, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃ or the like; the drying time is, for example, 8.2h, 8.5h, 8.8h, 9h, 9.2h, 9.5h, 9.8h, or the like.

Preferably, the current collector is a copper foil.

Preferably, the silicon carbon negative electrode material comprises silicon carbon 650 and/or silicon carbon 480.

Preferably, the conductive agent is super P.

Preferably, after the reaction pole piece is soaked into the reaction system in the step (2), a post-treatment process is further included.

Preferably, the post-treatment is vacuum drying.

Preferably, the drying temperature is 60-90 ℃, and the time is 8-10 h; the drying temperature is, for example, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃ or the like; the drying time is, for example, 8.2h, 8.5h, 8.8h, 9h, 9.2h, 9.5h, 9.8h, or the like.

As a preferred technical scheme, the preparation method of the electrode plate comprises the following steps:

(1) grinding and mixing a silicon-carbon negative electrode material, a water-based binder and a conductive agent, wherein the mass ratio of the silicon-carbon negative electrode material to the water-based binder to the conductive agent is 3-16: 1:1, adding water, stirring for 5-10 h to obtain an electrode slurry, coating the electrode slurry on a current collector, and performing vacuum drying at 60-90 ℃ for 8-10 h to obtain a silicon-carbon negative electrode piece;

(2) dissolving trihydroxymethyl aminomethane in water, and then adding acid to adjust the pH value to 7-9 to obtain a buffer solution;

(3) dissolving dopamine in a buffer solution, and adding an oxidant to obtain a reaction system, wherein the concentration of the dopamine in the reaction system is 1-5 g/L, the concentration of the oxidant is 10-30 mmol/L, and the concentration of tris (hydroxymethyl) aminomethane is 5-15 mmol/L;

(4) and infiltrating the silicon-carbon negative electrode plate into a reaction system for 0.1-1 h, wherein the temperature of the reaction system is 30-60 ℃, and vacuum drying is carried out for 8-10 h at the temperature of 60-90 ℃ to obtain the electrode plate.

The second purpose of the invention is to provide an electrode plate, which is prepared by the method of the first purpose.

Preferably, the electrode plate comprises a current collector, and an active material layer and a polydopamine material layer which are sequentially arranged on the surface of the current collector.

Preferably, the polydopamine material layer comprises any one or a combination of at least two of dopamine monomer, dihydroxyindole, indole dione and catechol derivative and polymer thereof.

The third object of the present invention is to provide the use of the electrode sheet of the second object for any one or a combination of at least two of lithium ion batteries, sodium ion batteries and potassium ion batteries.

Compared with the prior art, the invention has the following beneficial effects:

in the invention, a multifunctional group on dopamine is introduced on an electrode plate, and in the charging and discharging processes, the multi-electron amino attached to the surface of the electrode plate can promote the reduction of electrolyte and additives in electrolyte and promote the formation of a stable SEI film on the surface of the electrode, so that the electrolyte and the electrode can be separated as soon as possible to reduce contact; on the other hand, the co-embedding of solvent molecules can be prevented, and the damage to the electrode material structure can be reduced on both aspects, so that the generation of irreversible capacity is reduced, the cycle performance of the electrode is further improved, and the breakage and crushing of the electrode sheet caused by volume expansion in the charging and discharging processes are reduced. When the polymerization time is 40min, the optimal technical effect can be achieved, the first discharge specific capacity can reach 647mAh/g, the 100 th discharge specific capacity can reach 563mAh/g, and the capacity retention rate of 100 circles can reach 87%.

Drawings

FIG. 1 is a graph of specific discharge capacity of electrode sheets obtained in example 1 of the present invention and comparative example 1 after 100 cycles;

FIG. 2 is an impedance diagram of electrode sheets obtained in example 1 of the present invention and comparative example 1 after 200 cycles.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.