阅读说明：本技术 一种纺丝隔膜与电极的复合方法及其处理后的一体化结构 (Spinning diaphragm and electrode compounding method and integrated structure processed by same ) 是由 吴如森 于 2021-02-20 设计创作，主要内容包括：本发明属于锂离子电池材料技术领域,尤其涉及一种纺丝隔膜与电极的复合方法及其处理后的一体化结构,所述纺丝隔膜与电极的复合方法包括以下步骤：步骤一：用NMP溶解PVDF,真空搅拌机中搅拌至均一透明状,制成PVDF溶液；步骤二：将经步骤一混合后的溶液刷或喷涂在负极片表面；步骤三：再将纺丝隔膜贴在负极片的表面；步骤四：在一定压力下,通过温热辊压法,使纺丝隔膜与负极片复合成隔膜～电极片～隔膜的一体化结构模式。本发明提供一种将隔膜粘贴在负极,使纺丝隔膜与电极复合,改善锂离子电池制造工艺,使电池隔膜在卷装和电池组装过程中达到要求的纺丝隔膜与电极的复合方法及其处理后的一体化结构。(The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a spinning diaphragm and electrode compounding method and a treated integrated structure thereof, wherein the spinning diaphragm and electrode compounding method comprises the following steps: the method comprises the following steps: dissolving PVDF by NMP, and stirring in a vacuum stirrer to be uniform and transparent to prepare a PVDF solution; step two: brushing or spraying the solution mixed in the step one on the surface of the negative plate; step three: then the spinning diaphragm is attached to the surface of the negative plate; step four: under a certain pressure, the spinning diaphragm and the negative plate are compounded into an integrated structural mode of diaphragm-electrode plate-diaphragm by a warm rolling method. The invention provides a method for compounding a spinning diaphragm and an electrode and an integrated structure after treatment, which are used for pasting the diaphragm on a negative electrode, compounding the spinning diaphragm and the electrode, improving the manufacturing process of a lithium ion battery and enabling the battery diaphragm to meet the requirements in the processes of rolling and battery assembly.)

1. A spinning diaphragm and electrode compounding method is characterized in that: the spinning diaphragm and electrode compounding method comprises the following steps:

the method comprises the following steps: dissolving PVDF by NMP, and stirring in a vacuum stirrer to be uniform and transparent to prepare a PVDF solution;

step two: brushing or spraying the solution mixed in the step one on the surface of the negative plate;

step three: then the spinning diaphragm is attached to the surface of the negative plate;

step four: under a certain pressure, the spinning diaphragm and the negative plate are compounded into an integrated structural mode of diaphragm-electrode plate-diaphragm by a warm rolling method.

2. The spinning membrane and electrode compounding method of claim 1, wherein: the concentration of PVDF in the PVDF solution in the first step is 0.1-20 wt%.

3. The spinning membrane and electrode compounding method of claim 1, wherein: in the second step, the solution is brushed or sprayed on the surface of the whole negative plate, and the coating amount on the surface of the negative plate is as follows: 1 to 100g/m²The coating thickness is 1 to 5 μm.

4. The spinning membrane and electrode compounding method of claim 1, wherein: in the fourth step, the rolling temperature is 120-200 ℃, and the linear speed of the roll surface during rolling is 0.1-10 m/min.

5. The spinning membrane and electrode compounding method of claim 1, wherein: in the fourth step, pressure is applied according to the width L of the roller, and the set pressure per unit width is 0.1-100 Kg/m.

6. An integrated structure, characterized in that: the integrated structure is obtained by processing the spinning diaphragm and the electrode in the compound method of any one of claims 1 to 5.

Technical Field

The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a spinning diaphragm and electrode compounding method and an integrated structure after treatment.

Background

The prior art and the defects are as follows:

the lithium ion battery mainly comprises an anode, a cathode, a diaphragm, electrolyte and a shell, wherein the diaphragm is arranged between the anode and the cathode of the battery, so that the physical contact between the anode and the cathode is prevented from generating short circuit, and lithium ions are allowed to migrate between the anode and the cathode of the battery, thereby achieving the purpose of charging and discharging. The excellent degree of the battery performance depends on the performance of the diaphragm, so the development of the diaphragm material with good chemical stability, high mechanical strength, high porosity and good thickness uniformity has important significance for improving the battery performance.

The lithium ion battery diaphragm material can be divided into the following components according to different physical and chemical characteristics: woven films, non-woven fabrics, microporous films, composite films, diaphragm paper, rolled films and the like. Because the polyolefin material has the characteristics of excellent mechanical property, chemical stability and relative low price, the current commercial lithium battery diaphragm material mainly adopts polyolefin microporous membranes such as Polyethylene (PE), polypropylene (PP) and the like. However, the polyolefin separator has poor thermal stability and low porosity, which can cause high battery impedance, low energy density and low rate performance of the battery during charging and discharging. Meanwhile, the melting point of the polyolefin diaphragm is low, and when the internal temperature of the battery rises, the diaphragm is easy to shrink and melt by heating, and loses the isolation effect on the positive and negative electrode plates, so that safety accidents such as battery short circuit, fire, explosion and the like are caused. The polyolefin diaphragm of the commercial lithium ion battery has the defect of poor affinity with electrolyte, so that the electrolyte cannot be well wetted and permeated with the diaphragm, and dry areas are easily generated due to insufficient wetting of the electrolyte.

How to improve the porosity, thermal stability and liquid absorption rate of the separator is a subject of constant attention in the scientific and industrial fields at present. CN102437304A discloses a diaphragm and a method for preparing a composite electrode pair by using the diaphragm, wherein one side of the diaphragm is coated with a positive electrode mixture comprising a positive electrode active material, a conductive agent and an adhesive, the other side of the diaphragm is coated with a negative electrode mixture comprising a negative electrode active material, a conductive agent and an adhesive, and finally the diaphragm is prepared by foaming a foaming agent, so that the positive electrode and the negative electrode of a battery are prevented from being directly contacted. CN108305973A discloses a composite diaphragm with a coating, a preparation method and an application thereof, which comprises a basal membrane and a high-temperature resistant coating coated on at least one surface of the basal membrane, and the composite diaphragm can promote the absorption of battery electrolyte and can be better adhered to the surface of an electrode. CN110323075A discloses a diaphragm/electrode composite structure and a preparation method thereof, wherein a ceramic coating is prepared on one surface of the diaphragm, and then an electrode material layer is prepared on the other surface of the diaphragm or one surface of the ceramic coating, so as to obtain the diaphragm/electrode composite structure. CN111370627A discloses a method for directly compounding a metal lithium electrode and an inorganic solid electrolyte ceramic diaphragm, which enables lithium liquid to infiltrate and spread on the surface of the inorganic solid electrolyte ceramic diaphragm. However, the combination of the existing diaphragm and the electrode is limited by the material performance, the ceramic diaphragm is easy to fall off and is easy to decompose at high temperature.

CN103682247B proposes a method of spraying polyamic acid on a polar plate, and then mechanically rolling and heat treating to form a polyimide nanofiber membrane. The method realizes the close fit of the pole piece and the diaphragm by generating phase change through rolling and heat treatment. Patent CN110034337A is through hot pressing complex, and the diaphragm is pressed tightly together with positive negative pole piece, increases the intensity of pole piece, prevents to take absolutely when tensile. However, the above two patents are both simple to press the diaphragm and the pole piece together. The bonding strength between the diaphragm and the pole piece is low, and the diaphragm is easy to peel off.

Polyvinylidene fluoride (PVDF) has the characteristics of good thermal stability, excellent electrochemical stability, good film forming property and the like, and becomes a main research object of lithium ion battery separators. At present, researchers adopt an electrostatic spinning method to prepare the lithium ion battery diaphragm, and the electrochemical performance of the lithium ion battery diaphragm is improved. The spinning nanofiber membrane has the advantages of small diameter, large specific surface area, high ionic conductivity, high porosity, small and uniform pore diameter. Therefore, the prepared spinning diaphragm has high liquid absorption rate and lithium ion conductivity, so that excellent electrochemical performance is achieved. Main polymer matrixes of the lithium ion battery diaphragm prepared by the electrostatic spinning technology comprise polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyimide and the like. The electrostatic spinning technology is that under the action of a strong electric field, a macromolecule solution or a solution in a molten state is branched and split to form countless uniform and continuous nano-fiber yarns, and the nano-fiber yarns are mutually stacked to form a fiber film. However, the tensile strength of the electrospun nanofiber membrane is poor, and high-speed winding is difficult to perform in the battery manufacturing process.

The difficulty and significance for solving the technical problems are as follows:

therefore, based on the existing problems, the technical method is provided for pasting the diaphragm on the surface of the negative electrode, compounding the spinning diaphragm with the electrode and simplifying the manufacturing process of the lithium ion battery. The invention simplifies the traditional winding process of the cathode, the diaphragm and the anode into the winding process of the coated cathode and the anode. The strength of the negative plate is improved, facilities for adjusting the tension of the diaphragm, unreeling the diaphragm, aligning the diaphragm and the like in the winding device are omitted, the manufacturing cost and the cost are greatly reduced, control points of the battery diaphragm in the processes of rolling and battery assembling are reduced, and the reliability and the stability are improved. The spinning diaphragm and electrode compounding method and the processed integrated structure thereof provided by the invention have important practical significance.

Disclosure of Invention

The invention aims to provide a method for compounding a spinning diaphragm and an electrode and an integrated structure after treatment, which are used for adhering the diaphragm to a negative electrode, compounding the spinning diaphragm and the electrode, improving the manufacturing process of a lithium ion battery and enabling the battery diaphragm to meet the requirements in the processes of rolling and battery assembly.

The technical scheme adopted by the invention for solving the technical problems in the prior art is as follows:

the spinning diaphragm and electrode compounding method comprises the following steps:

the method comprises the following steps: dissolving PVDF (polyvinylidene fluoride) by NMP (N-methyl pyrrolidone), and stirring in a vacuum stirrer to be uniform and transparent to prepare a PVDF solution;

step two: brushing or spraying the solution mixed in the step one on the surface of the negative plate;

step three: then the spinning diaphragm is attached to the surface (double surfaces) of the negative plate;

step four: under a certain pressure, the spinning diaphragm and the negative plate are compounded into an integrated structural mode of diaphragm-electrode plate-diaphragm by a warm rolling method.

In the invention, the PVDF is softened by actually warming the pressure and temperature of the rolling, and the high-strength combination of the spinning diaphragm and the electrode is realized by utilizing the adhesion effect and the pressure effect of the PVDF in the subsequent cooling process. This effect produces a structure with a strength that is much higher than the composite achieved by mere hot pressing as mentioned in the reference. PVDF is selected, and the adhesive is mainly stable in chemical property and reliable in adhesion. And the PVDF solution of the patent has the function of surface covering while playing the role of a binder.

The invention can also adopt the following technical scheme:

in the method for combining the spinning diaphragm and the electrode, furthermore, the concentration of PVDF in the PVDF solution in the first step is 0.1-20 wt%.

In the above method for combining the spinning separator and the electrode, further, in the second step, the solution is brushed or sprayed on the surface of the whole negative electrode sheet, and the coating amount on the surface of the negative electrode is as follows: 1 to 100g/m²The coating thickness is 1 to 5 μm.

In the method for compounding the spinning diaphragm and the electrode, further, in the fourth step, the rolling temperature is 120-200 ℃, and the linear speed of the roller surface during rolling is 0.1-10 m/min.

In the method for combining the spinning diaphragm and the electrode, in the fourth step, pressure is applied according to the width L of the roller, and the unit width setting pressure is 0.1-100 Kg/m.

An integrated structure is obtained by processing the spinning diaphragm and the electrode by the composite method.

In conclusion, the invention has the following advantages and positive effects:

1. the invention provides a lithium ion battery diaphragm and electrode compounding technology, which overcomes the defects of low strength and difficult winding of an electrostatic spinning diaphragm in the prior art by forming a diaphragm-electrode plate-diaphragm structural mode, and simultaneously, the technology combines the diaphragm and a negative electrode, improves the assembly reliability, reduces the original structure of a positive electrode-diaphragm-negative electrode into a structure of a composite negative electrode plate-positive electrode, greatly simplifies the operation difficulty of equipment, and improves the reliability of a battery assembly system. In the lithium ion battery system, the cathode covers the anode, so the invention adopts the coated cathode and can completely realize the isolation of the anode and the cathode.

Detailed Description

Example 1

A spinning diaphragm and electrode compounding method and process comprises the following steps:

(1) dissolving PVDF in NMP to obtain 0.1 wt% mixed solution, and stirring in vacuum stirrer (rotating speed of 15r/min, 30 deg.C for 1.5 hr) to obtain homogeneous transparent solution, and mixing the two solutions.

(2) Uniformly brushing the mixed solution on the surface of a negative electrode through a coating machine, wherein the coating weight is 1g/m²The coating thickness was 1 μm.

(3) And attaching the prepared spinning diaphragm to the surface (double surfaces) of the negative plate.

(4) Passing through a roller press at a roll surface temperature of 120 ℃ under a pressure of 0.1 Kg/m. And (4) rolling. The linear velocity of the outer diameter of the roller is 0.1m/min, so that the diaphragm and the electrode are compounded into an integrated structural mode of diaphragm-electrode plate-diaphragm.

Example 2

A spinning diaphragm and electrode compounding method and process comprises the following steps:

(1) dissolving PVDF in NMP to obtain a mixed solution containing 20 wt% of PVDF, and stirring in a vacuum stirrer (rotating speed of 15r/min, and stirring at 30 deg.C for 2.5h) to obtain a uniform transparent solution, and mixing the two solutions thoroughly.

(2) Uniformly brushing the mixed solution on the surface of a negative electrode through a coating machine, wherein the coating weight is 100g/m²The coating thickness was 5 μm.

(3) And attaching the prepared spinning diaphragm to the surface (double surfaces) of the negative plate.

(4) Under the pressure of 100Kg/m, the diaphragm and the electrode are compounded into an integrated structure of diaphragm-electrode plate-diaphragm by a warm rolling method (200 ℃, the outer diameter linear velocity of the roller is 10 m/min).

The prepared composite diaphragm electrode is used for the subsequent preparation of the lithium ion battery.

Example 3

A spinning diaphragm and electrode compounding method and process comprises the following steps:

(1) dissolving PVDF in NMP to obtain a mixed solution containing 10 wt% of PVDF, and stirring in a vacuum stirrer (rotating speed of 15r/min, and stirring at 30 deg.C for 2h) to obtain a uniform and transparent solution, and mixing the two solutions thoroughly.

(2) After mixingThe solution is uniformly brushed on the surface of the negative electrode by a coating machine, and the coating weight is 30g/m²The coating thickness was 3 μm.

(3) And attaching the prepared spinning diaphragm to the surface (double surfaces) of the negative plate.

(4) Under the pressure of 20Kg/m, the diaphragm and the electrode are compounded into an integrated structure of diaphragm-electrode plate-diaphragm by a warm rolling method (140 ℃ and the linear speed of the roller is 4 m/min).

Example 4

A spinning diaphragm and electrode composite method and the contrast effect of the process are as follows:

the method A comprises the following steps:

(1) dissolving PVDF in NMP to obtain 12 wt% mixed solution, and stirring in vacuum stirrer (rotating speed of 15r/min, 30 deg.C for 2 hr) to obtain homogeneous transparent mixture.

(2) Uniformly brushing the mixed solution on the surface of a negative electrode through a coating machine, wherein the coating weight is 10g/m²The coating thickness was 8 μm.

(3) And attaching the prepared spinning diaphragm to the surface (double surfaces) of the negative plate.

(4) Under the pressure of 20Kg/m, the diaphragm and the electrode are compounded into an integrated structure of diaphragm-electrode plate-diaphragm by a warm rolling method (150 ℃ and the linear speed of the roller of 6 m/min).

The method B comprises the following steps:

(1) and attaching the prepared spinning diaphragm to the surface (double surfaces) of the negative plate.

(2) Under the pressure of 20Kg/m, the diaphragm and the electrode are compounded into an integrated structure of diaphragm-electrode plate-diaphragm by a warm rolling method (150 ℃ and the linear speed of the roller of 6 m/min).

Ternary system lithium ion batteries, model ICR18650-3.6V-2200mAh, were made using Process A and Process B, respectively. The test of the battery system shows that the capacity retention rate of the battery sample prepared by the process A is 81 percent after 2000 times of circulation. And the capacity of the battery sample prepared by the process B is reduced to about 80 percent after 750 times of circulation. It can be seen that process a, which includes all the technical features of the present invention, is of significant advancement.

In summary, the present invention provides a method for compounding a spinning separator and an electrode, which comprises adhering the separator to a negative electrode, compounding the spinning separator and the electrode, improving the manufacturing process of a lithium ion battery, and making the battery separator meet the requirements in the processes of rolling and battery assembly, and an integrated structure after the processing.

The present invention has been described in detail with reference to the above examples, but the description is only for the preferred examples of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.