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Application of dry screw vacuum pump in lithium battery production process Nov 07, 2022

锂电池的生产工艺比较复杂,主要生产工艺主要包括电极生产的搅拌和涂覆阶段(前段)、电池合成的缠绕和注入阶段(中段)、化成包装的包装检验阶段(后段)。

锂电池的前端生产过程关系到电池在极片制造中的核心性能,相应的锂电池设备主要包括真空搅拌机、涂布机、辊压机等。

锂电池前端工艺的结果是制备锂电池正负极片,其第一道工序是搅拌,即将固态电池正负极材料混合均匀,然后加入溶剂,通过真空混合器搅拌成浆料。成分的混合是锂电池后续工艺的基础,搅拌是完成后续涂装和轧制工艺的基础。

涂层和轧制过程之后是分切,即涂层经过分切过程。如果在分切过程中出现毛刺,则在随后的组装,电解液注入和其他过程中,甚至在电池使用过程中都会发生潜在的事故。因此,锂电池生产过程中的前端设备,如搅拌机、涂布机、辊压机、分条机等,都是电池制造的核心机器,关系到整条生产线的质量。

锂电池生产中的真空应用说明

电极材料制浆搅拌、材料输送和储存真空脱气

1、在锂电池生产过程初期的制浆过程中,需要对电极浆料进行真空脱气,实现极辊涂布;

2.泵送气体是含有一定量水蒸气和有机溶剂NMP挥发物(腐蚀铜)和残余材料粉尘的混合气体,因此,螺杆干式真空泵要求具有较强的特殊介质处理能力;

3.一般粉尘颗粒的直径为0.1~10微米,而目前好的真空泵过滤器只能捕获大于2微米左右的颗粒,因此过滤器不能有效地过滤和拦截粉尘(使用2微米过滤器会影响真空泵的抽速),例如使用油封真空泵会频繁换油而失效;使用液环真空泵的真空度不够,只能长时间保持-85KPa的真空度,脱气不能满足工艺的需要,但实际应用工艺一般要求-95Kpa左右;

4.多采用螺杆干式真空泵来应对这一过程,其性能远远优于爪式干式真空泵和多级罗茨真空泵,设备抽真空只需要一台螺杆真空泵,无需配置罗茨泵来增加压力和速度。但正负极应分开配备真空抽真空,如需组合同一真空系统抽真空,使用时必须配置真空阀,严格控制单次单独抽真空;

5. 干式真空泵特性比较

 

type

 

Claw vacuum pump

(Multi-level roots analogy)

Screw dry vacuum pump

Ultimate vacuum

Around 1-5Pa

0.5-1Pa

Process performance

Moderate satisfaction

Can be fully satisfied

Vacuum pressure stability

good

very good

Dust removal capacity

weak

 

Drainage capacity

weak

 

Supplies

Gear oil

Gear oil

Corrosion resistance

The rotor and vacuum chamber are ductile iron, which need to be coated

The rotor and vacuum chamber are ductile iron, which need to be coated with strong corrosion resistance

Maintenance

high

Low, 30% lower than the former.

Maintenance

Short-term maintenance, but long-term use in dust, liquid process is prone to failure, service life of about 8 years

Almost maintenance-free, maintenance can be carried out once in about 2-3 years, and the design life is about 12 years.

Price

high

High (similar to the former)

Difference in reliability of use

 

1. Due to the existence of a step spacer, the rotor and the pump shaft can not become one, the rotor is installed on the shaft later, in order to install and disassemble conveniently, the fit can not be too tight, so it is easy to have roller keys and loose rotor after operation.

2. There are many gaps, and each gap is standing, as long as there is a problem in any gap, the pump cannot work normally.

 

1. The shaft and rotor of the screw vacuum pump are processed and formed after casting as a whole, which is fully integrated and there is no assembly problem.

2. The outer circular gap of the screw vacuum pump and the gap between the exhaust end and the rotor determine the working performance, and the gap between the rotor and the rotor is interrelated and reliable.

Repair disassembly

 

Difficult disassembly of claw pumps: Due to the multi-stage structure, all disassembly requires multi-stage decomposition, and rotor disassembly is the real difficulty, and every time it is disassembled, the accuracy will be reduced to varying degrees. Even simple cleaning is all disassembled and reassembled.

Simple screw vacuum pump disassembly: The removal of the screw pump only requires removing the back cover bearing to extract the rotor from the front end, which is extremely simple. If it is only for cleaning and disassembly, after cleaning, simply put the rotor back into the pump body without any adjustments.

Repair assembly

 

Difficult assembly of claw pump: when the claw pump is installed, the 4-stage rotor should control the 8 gaps on the rotor end face, as well as the clearance between the rotor and the rotor of the 8 rotors, and any gap adjustment is not good to rework, want to install the rotor on the shaft, but also knock on the rotor, easy to damage the parts.

Simple assembly of screw vacuum pump: When assembling the screw pump, you only need to control the gap between the screw exhaust end face and the exhaust wall, as well as the gap between the screw concave surface, and only need to adjust the simple two gaps

 

 

 

 

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