阅读说明：本技术 硅负极中复合粘结剂的工艺方法及锂离子电池的制备方法 (Process method of composite binder in silicon cathode and preparation method of lithium ion battery ) 是由 许晓雄 丁超 魏引利 于 2020-12-01 设计创作，主要内容包括：本发明公开了一种硅负极中复合粘结剂的工艺方法及锂离子电池的制备方法,以0～0.8质量份的CMC、96质量份的硅碳负极和1.4质量份的SP通过机械搅拌器充分混合均匀,得到混合粉体；向混合粉体加入1～4质量份的PAA作为溶剂,通过机械搅拌器搅拌均匀,然后再加入0.2～1质量份的SBR溶液,并通过机械搅拌器充分混合均匀,形成浆料一；将浆料一均匀涂覆在集流体铜箔的双侧表面,真空干燥后用辊压机进行辊压、冲切,制备得到负极片。通过调整粘结剂的添加量和制备工序,改善硅负极的制作工艺,优化实际使用效果。(The invention discloses a process method of a composite binder in a silicon negative electrode and a preparation method of a lithium ion battery, wherein 0-0.8 part by mass of CMC, 96 parts by mass of a silicon-carbon negative electrode and 1.4 parts by mass of SP are fully and uniformly mixed by a mechanical stirrer to obtain mixed powder; adding 1-4 parts by mass of PAA (poly (acrylic acid)) serving as a solvent into the mixed powder, uniformly stirring by using a mechanical stirrer, then adding 0.2-1 part by mass of SBR solution, and fully and uniformly mixing by using the mechanical stirrer to form a first slurry; and uniformly coating the first slurry on the surfaces of the two sides of the copper foil of the current collector, performing vacuum drying, and then rolling and punching by using a roller press to prepare the negative plate. By adjusting the addition amount and preparation process of the binder, the manufacturing process of the silicon cathode is improved, and the actual use effect is optimized.)

1. The process method for compounding the binder in the silicon cathode is characterized by comprising the following steps of: the method comprises the following steps:

1) fully and uniformly mixing 0-0.8 part by mass of CMC, 96 parts by mass of silicon-carbon negative electrode and 1.4 parts by mass of SP through a mechanical stirrer to obtain mixed powder;

2) adding 1-4 parts by mass of PAA (poly (acrylic acid) serving as a solvent into the mixed powder obtained in the step 1), uniformly stirring by using a mechanical stirrer, then adding 0.2-1 part by mass of SBR (styrene butadiene rubber) solution, and fully and uniformly mixing by using the mechanical stirrer to form a first slurry;

3) uniformly coating the slurry I obtained in the step 2) on the surfaces of the two sides of the current collector copper foil, carrying out vacuum drying, and then carrying out rolling and punching by using a roller press to prepare the negative plate.

2. The process method for compounding the binder in the silicon negative electrode as claimed in claim 1, wherein: after the PAA is added in the step 2), the shear rate of the mechanical stirrer is 10m/s, and after the SBR solution is added, the shear rate of the mechanical stirrer is 5 m/s.

3. The process method for compounding the binder in the silicon negative electrode as claimed in claim 1, wherein: the thickness of the current collector copper foil in the step 3) is 9 um.

4. The process method for compounding the binder in the silicon negative electrode as claimed in claim 3, wherein: the drying temperature of the current collector copper foil coated with the slurry I in the step 3) is 85 +/-5 ℃, and the drying time is 16 h.

5. The preparation method of the lithium ion battery is characterized by comprising the following steps: the method comprises the following steps:

step one, preparing a negative plate

Fully and uniformly mixing 0-0.8 mass part of CMC, 96 mass parts of silicon-carbon negative electrode and 1.4 mass parts of SP through a mechanical stirrer to obtain mixed powder, adding 1-4 mass parts of PAA serving as a solvent into the mixed powder, uniformly stirring through the mechanical stirrer, then adding 0.2-1 mass part of SBR solution, fully and uniformly mixing through the mechanical stirrer to form a slurry I, uniformly coating the obtained slurry I on the surfaces of two sides of a current collector copper foil, carrying out rolling and punching through a roller press after vacuum drying, and preparing a negative plate;

step two, preparing the positive plate

Sequentially adding 3 parts by mass of PVDF, 2 parts by mass of CNT, 1 part by mass of SP and 94 parts by mass of NCM positive electrode material into 50 parts by mass of NMP serving as a solvent, uniformly stirring by using a mechanical stirrer to form a second slurry, uniformly coating the two side surfaces of an aluminum foil with the second slurry, carrying out vacuum drying, and then carrying out rolling and punching by using a roller press to prepare a positive electrode plate;

step three, preparing the lithium ion battery

And assembling the positive plate, the negative plate and the diaphragm, and injecting electrolyte to obtain the lithium ion battery.

6. The method for producing a lithium ion battery according to claim 5, characterized in that: after the PAA is added in the first step, the shear rate of a mechanical stirrer is 10m/s, and after the SBR solution is added, the shear rate of the mechanical stirrer is 5 m/s; the thickness of the current collector copper foil in the first step is 9 um; in the step one, the drying temperature of the current collector copper foil coated with the slurry I is 85 +/-5 ℃, and the drying time is 16 h.

7. The method for producing a lithium ion battery according to claim 5, characterized in that: the thickness of the copper foil in the second step is 14 um; and in the second step, the drying temperature of the copper foil coated with the second slurry is 100 +/-5 ℃, and the drying time is 16 h.

8. The method for producing a lithium ion battery according to claim 5, characterized in that: and step three, laminating the positive plates, the diaphragms and the negative plates alternately in a Z-shaped lamination mode to form a battery cell, welding and packaging the obtained battery cell with an aluminum-plastic film, injecting electrolyte and sealing, and then preparing the soft package lithium ion battery.

9. The method for producing a lithium ion battery according to claim 8, characterized in that: the diaphragm is a double-sided coated nano ceramic diaphragm, and the thickness of the diaphragm is 29 um.

10. The method for producing a lithium ion battery according to claim 5, characterized in that: the electrolyte salt in the electrolyte is LiPF6, the organic solvent of the electrolyte is an EC/EMC/DMC/PC mixed solvent system, the volume ratio of EC/EMC/DMC is 1:1:1, PC accounts for 0.3% of the total weight of the electrolyte, the additive in the electrolyte is VC, and VC accounts for 1.5% of the total weight of the electrolyte.

Technical Field

The invention relates to a lithium ion battery, in particular to a process method of a composite binder in a silicon cathode and a preparation method of the lithium ion battery.

Background

The lithium ion battery has the advantages of high energy density, excellent multiplying power and power performance, long cycle life, safety, environmental protection and the like, so that the lithium ion battery is widely applied to daily life as an important chemical power source.

With the continuous development of the lithium ion battery industry, the performance requirements of the binder are also continuously improved. The power type lithium ion battery has high discharge power, so that the binder has good binding property and good electronic and ionic conductivity. In order to maintain the stability of the electrode structure, the binder should have good elasticity to buffer the volume effect.

Therefore, the novel high-performance binder for the lithium ion battery has become one of important development directions for the research and development of the lithium ion battery key material. In recent years, the research on novel binders for lithium ion batteries includes polymer and derivatives thereof, natural extract binders, conductive binders and self-repairing binders, and the development prospect of the novel binders for lithium ion batteries is expected.

In recent years, silicon negative electrode materials have attracted much attention at home and abroad, and are considered to be ideal candidate materials for next-generation high-specific-energy lithium ion batteries. But the serious volume expansion effect and cycle attenuation of the lithium ion battery cell are not negligible in the charging and discharging process, and active material particles are cracked and pulverized due to volume expansion and even stripped from a current collector, so that the battery cell is in cyclic failure. Therefore, the binder plays a crucial role in application research of silicon negative electrodes as a connecting bridge between active substances and between the active substances and a current collector, and when the novel composite binder system is used, due to the influence of the addition sequence and the active substance particle size matching property, a plurality of problems such as agglomeration, sedimentation and the like exist in the actual use process, and the actual use effect is poor.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a process method of a composite binder in a silicon cathode and a preparation method of a lithium ion battery, wherein the manufacturing process of the silicon cathode is improved and the actual using effect is optimized by adjusting the addition amount and the preparation process of the binder.

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

the process method for compounding the binder in the silicon negative electrode comprises the following steps:

1) fully and uniformly mixing 0-0.8 part by mass of CMC, 96 parts by mass of silicon-carbon negative electrode and 1.4 parts by mass of SP through a mechanical stirrer to obtain mixed powder;

2) adding 1-4 parts by mass of PAA (poly (acrylic acid) serving as a solvent into the mixed powder obtained in the step 1), uniformly stirring by using a mechanical stirrer, then adding 0.2-1 part by mass of SBR (styrene butadiene rubber) solution, and fully and uniformly mixing by using the mechanical stirrer to form a first slurry;

3) uniformly coating the slurry I obtained in the step 2) on the surfaces of the two sides of the current collector copper foil, carrying out vacuum drying, and then carrying out rolling and punching by using a roller press to prepare the negative plate.

Preferably, the shear rate of the mechanical stirrer is 10m/s after the PAA is added in the step 2), and the shear rate of the mechanical stirrer is 5m/s after the SBR solution is added.

Preferably, the thickness of the copper foil of the current collector in the step 3) is 9 um.

Preferably, the drying temperature of the copper foil of the current collector coated with the slurry I in the step 3) is 85 ℃ +/-5 ℃, and the drying time is 16 h.

The preparation method of the lithium ion battery comprises the following steps:

step one, preparing a negative plate

Fully and uniformly mixing 0-0.8 mass part of CMC, 96 mass parts of silicon-carbon negative electrode and 1.4 mass parts of SP through a mechanical stirrer to obtain mixed powder, adding 1-4 mass parts of PAA serving as a solvent into the mixed powder, uniformly stirring through the mechanical stirrer, then adding 0.2-1 mass part of SBR solution, fully and uniformly mixing through the mechanical stirrer to form a slurry I, uniformly coating the obtained slurry I on the surfaces of two sides of a current collector copper foil, carrying out vacuum drying, and then carrying out rolling and punching through a roller press to prepare a negative plate;

step two, preparing the positive plate

Sequentially adding 3 parts by mass of PVDF, 2 parts by mass of CNT, 1 part by mass of SP and 94 parts by mass of NCM positive electrode material into 50 parts by mass of NMP serving as a solvent, uniformly stirring by using a mechanical stirrer to form a second slurry, uniformly coating the two side surfaces of an aluminum foil with the second slurry, performing vacuum drying, and then performing rolling and punching by using a roller press to prepare a positive electrode sheet;

step three, preparing the lithium ion battery

And assembling the positive plate, the negative plate and the diaphragm, and injecting electrolyte to obtain the lithium ion battery.

Preferably, after the PAA is added in the step one, the shear rate of a mechanical stirrer is 10m/s, and after the SBR solution is added, the shear rate of the mechanical stirrer is 5 m/s; the thickness of the current collector copper foil in the first step is 9 um; in the step one, the drying temperature of the current collector copper foil coated with the slurry I is 85 +/-5 ℃, and the drying time is 16 h.

Preferably, the thickness of the copper foil in the second step is 14 um; and in the second step, the drying temperature of the copper foil coated with the second slurry is 100 +/-5 ℃, and the drying time is 16 h.

Preferably, in the third step, in a Z-shaped lamination mode, the positive plate, the diaphragm and the negative plate are alternately laminated to form a battery cell, and then the obtained battery cell is welded and packaged by an aluminum plastic film, and then the electrolyte is injected and sealed, so that the soft package lithium ion battery is prepared.

Preferably, the diaphragm is a nano ceramic diaphragm coated on two sides and has the thickness of 29 um.

Preferably, the electrolyte salt in the electrolyte is LiPF6, the organic solvent of the electrolyte is an EC/EMC/DMC/PC mixed solvent system, the volume ratio of EC/EMC/DMC is 1:1:1, PC accounts for 0.3% of the total weight of the electrolyte, the additive in the electrolyte is VC, and VC accounts for 1.5% of the total weight of the electrolyte.

Compared with the prior art, the process method for compounding the binder in the silicon negative electrode and the preparation method of the lithium ion battery have the advantages that:

by adjusting the addition amount and the preparation process of the binder, the preparation process of the silicon cathode is improved, and the volume expansion rate of the lithium ion battery packaged by the aluminum-plastic film can be controlled to be 6-8%, so that the actual requirement is met, the problems of agglomeration, sedimentation and the like are avoided in the actual use process, and the actual use effect of the lithium ion battery is optimized.

Detailed Description

The following examples further describe the invention in detail.

The preparation method of the lithium ion battery comprises the following steps:

step one, preparing a negative plate

Fully and uniformly mixing 0-0.8 mass part of CMC, 96 mass parts of silicon-carbon negative electrode and 1.4 mass parts of SP through a mechanical stirrer of a double-star power mixer to obtain mixed powder, adding 1-4 mass parts of PAA serving as a solvent into the mixed powder, uniformly stirring through the mechanical stirrer of the double-star power mixer, then adding 0.2-1 mass part of SBR solution, fully and uniformly mixing through the mechanical stirrer of the double-star power mixer to form a slurry I, uniformly coating the obtained slurry I on the surfaces of two sides of a current collector copper foil, performing rolling and punching through a roller press after vacuum drying, and preparing a negative plate;

step two, preparing the positive plate

Sequentially adding 3 parts by mass of PVDF, 2 parts by mass of CNT, 1 part by mass of SP and 94 parts by mass of NCM positive electrode material by taking 50 parts by mass of NMP as a solvent, uniformly stirring by using a mechanical stirrer of a double star power mixer to form a second slurry, uniformly coating the obtained second slurry on the surfaces of two sides of an aluminum foil, and carrying out rolling and punching by using a roller press after vacuum drying to prepare a positive electrode sheet;

step three, preparing the lithium ion battery

And (3) laminating the positive plate, the diaphragm and the negative plate alternately to form a battery cell in a Z-shaped lamination mode, welding and packaging the obtained battery cell with an aluminum-plastic film, injecting electrolyte and sealing, and further preparing the soft package lithium ion battery.

After the PAA is added in the first step, the shear rate of the mechanical stirrer is 10m/s, and after the SBR solution is added, the shear rate of the mechanical stirrer is 5 m/s. The thickness of the current collector copper foil in the first step is 9 um; in the step one, the drying temperature of the current collector copper foil coated with the slurry I is 85 +/-5 ℃, and the drying time is 16 h.

The thickness of the copper foil in the second step is 14 um; and in the second step, the drying temperature of the copper foil coated with the second slurry is 100 +/-5 ℃, and the drying time is 16 h.

The diaphragm in the third step is a nano ceramic diaphragm coated on two sides, and the thickness of the diaphragm is 29 um. Electrolyte salt in the electrolyte in the third step is LiPF6, the organic solvent of the electrolyte is an EC/EMC/DMC/PC mixed solvent system, wherein the volume ratio of EC/EMC/DMC is 1:1:1, PC accounts for 0.3% of the total weight of the electrolyte, and the additive in the electrolyte is VC which accounts for 1.5% of the total weight of the electrolyte.

Examples 1,

The preparation method of the lithium ion battery comprises the following steps:

step one, preparing a negative plate

Fully and uniformly mixing 0.1 part by mass of CMC, 96 parts by mass of silicon-carbon negative electrode and 1.4 parts by mass of SP through a mechanical stirrer of a double-star power mixer to obtain mixed powder, adding 2 parts by mass of PAA serving as a solvent into the mixed powder, and uniformly stirring at a high speed through the mechanical stirrer, wherein the shearing rate is 10 m/s. Then adding 0.5 part by mass of SBR solution, fully and uniformly mixing the solution by a mechanical stirrer of a double-star power mixer at a shearing rate of 5m/s to form a first slurry, uniformly coating the obtained first slurry on the surfaces of two sides of a current collector copper foil with the thickness of 9um, drying the copper foil in vacuum at 85 ℃ for 16 hours, and then rolling and punching the copper foil by using a roller press to prepare a negative plate;

step two, preparing the positive plate

Sequentially adding 3 parts by mass of PVDF, 2 parts by mass of CNT, 1 part by mass of SP and 94 parts by mass of NCM positive electrode material by taking 50 parts by mass of NMP as a solvent, uniformly stirring by using a mechanical stirrer of a double star power mixer to form a second slurry, uniformly coating the obtained second slurry on the two side surfaces of an aluminum foil with the thickness of 14 microns, carrying out vacuum drying at 100 ℃ for 16 hours, and then carrying out rolling and punching by using a rolling machine to prepare a positive electrode sheet;

step three, preparing the lithium ion battery

And (3) laminating the positive plate, the diaphragm and the negative plate alternately to form a battery cell in a Z-shaped lamination mode, welding and packaging the obtained battery cell with an aluminum-plastic film, injecting electrolyte and sealing, and further preparing the soft package lithium ion battery.

The diaphragm in the third step is a nano ceramic diaphragm coated on two sides, and the thickness of the diaphragm is 29 um. Electrolyte salt in the electrolyte in the third step is LiPF6, the organic solvent of the electrolyte is an EC/EMC/DMC/PC mixed solvent system, wherein the volume ratio of EC/EMC/DMC is 1:1:1, PC accounts for 0.3% of the total weight of the electrolyte, and the additive in the electrolyte is VC which accounts for 1.5% of the total weight of the electrolyte.

Examples 2,

The preparation method of the lithium ion battery comprises the following steps:

step one, preparing a negative plate

Fully and uniformly mixing 0.8 mass part of CMC, 96 mass parts of silicon-carbon negative electrode and 1.4 mass parts of SP through a mechanical stirrer of a double-star power mixer to obtain mixed powder, adding 1 mass part of PAA serving as a solvent into the mixed powder, and uniformly stirring at a high speed through the mechanical stirrer, wherein the shearing rate is 10 m/s. Then adding 0.2 part by mass of SBR solution, fully and uniformly mixing the solution by a mechanical stirrer of a double-star power mixer at a shearing rate of 5m/s to form a first slurry, uniformly coating the obtained first slurry on the surfaces of two sides of a current collector copper foil with the thickness of 9um, drying the copper foil in vacuum at 85 ℃ for 16 hours, and then rolling and punching the copper foil by using a roller press to prepare a negative plate;

the process for preparing the positive plate in the second step and the process for preparing the lithium ion battery in the third step are not changed, and are the same as the example 1.

Comparative examples 1,

The preparation method of the lithium ion battery comprises the following steps:

step one, preparing a negative plate

And (2) fully and uniformly mixing 96 parts by mass of a silicon-carbon negative electrode and 1.4 parts by mass of SP through a mechanical stirrer of a double-star power mixer to obtain mixed powder, adding 4 parts by mass of PAA (poly (acrylic acid)) serving as a solvent into the mixed powder, and uniformly stirring at a high speed through the mechanical stirrer, wherein the shearing rate is 10 m/s. Then adding 1 part by mass of SBR solution, fully and uniformly mixing the solution by a mechanical stirrer of a double-star power mixer at a shearing rate of 5m/s to form a first slurry, uniformly coating the obtained first slurry on the surfaces of two sides of a current collector copper foil with the thickness of 9um, carrying out vacuum drying at 85 ℃ for 16 hours, and then carrying out rolling and punching by using a rolling machine to prepare a negative plate;

the process for preparing the positive plate in the second step and the process for preparing the lithium ion battery in the third step are not changed, and are the same as the example 1.

Comparative examples 2,

The preparation method of the lithium ion battery comprises the following steps:

step one, preparing a negative plate

0.1 part by mass of CMC, 96 parts by mass of silicon-carbon negative electrode, 1.4 parts by mass of SP and 2 parts by mass of PAA solvent are uniformly stirred at high speed by a mechanical stirrer of a double-star power mixer, and the shear rate is 10 m/s. Then adding 0.5 part by mass of SBR solution, fully and uniformly mixing the solution by a mechanical stirrer of a double-star power mixer at a shearing rate of 5m/s to form a first slurry, uniformly coating the obtained first slurry on the surfaces of two sides of a current collector copper foil with the thickness of 9um, drying the copper foil in vacuum at 85 ℃ for 16 hours, and then rolling and punching the copper foil by using a roller press to prepare a negative plate;

the process for preparing the positive plate in the second step and the process for preparing the lithium ion battery in the third step are not changed, and are the same as the example 1.

Comparative examples 3,

The preparation method of the lithium ion battery comprises the following steps:

step one, preparing a negative plate

Fully and uniformly mixing 0.1 part by mass of CMC, 96 parts by mass of silicon-carbon negative electrode, 1.4 parts by mass of SP, 2 parts by mass of PAA solvent and 0.5 part by mass of SBR solution by a mechanical stirrer of a double-star power mixer, wherein the shearing rate is 10m/s to form a first slurry, uniformly coating the obtained first slurry on the surfaces of two sides of a current collector copper foil with the thickness of 9um, carrying out vacuum drying at 85 ℃ for 16h, and then carrying out rolling and punching by using a roller press to prepare a negative plate;

the process for preparing the positive plate in the second step and the process for preparing the lithium ion battery in the third step are not changed, and are the same as the example 1.

The following table was obtained by comparing the performance of the lithium ion batteries prepared in examples 1 and 2 and comparative examples 1, 2 and 3.

As can be seen from the above table, since the lithium ion battery in this embodiment is packaged by using an aluminum plastic film, the volume expansion rate should be in the range of 6% to 8%, and when the mass part of the added CMC reaches 0.8, the volume expansion rate of the prepared lithium ion battery exceeds 8%, which is undesirable, and therefore the mass part range of the CMC is preferably between 0 to 0.8.

As can be seen from the above table, the capacity retention rate and the volume expansion rate of the lithium ion battery prepared in example 1 are superior to those of the lithium ion batteries prepared in comparative examples 1 to 3, and can meet the use requirements, and simultaneously can avoid the problems of agglomeration, sedimentation and the like during use.

Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that modifications and variations of the present invention are possible to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.