3.7V Lithium Polymer Battery intelligent manufacturing back-end processing technology

In recent years, with the rapid development of the new energy industry, the continuous upgrading of new energy vehicles and power battery industries, battery factories have higher and higher requirements for automation and compatibility.

On December 27-28, the "2017 APEC New Energy Vehicle & 3.7V Lithium Polymer Battery Leaders Summit and the Third Qidian Golden Tripod Award Ceremony" hosted by Qidian Research, 3.7V Lithium Polymer Battery Big Data, and Qidian Electric Network was held in the Julong Hall of the Crowne Plaza Pearl River in Longgang, Shenzhen.

More than 1,000 elite senior executives from vehicle companies, core component companies, and parts companies gathered together to discuss new cooperation models, strengthen the deep integration of the new energy vehicle industry chain, and promote the healthy development of the industry.

Zhao Shaohua, vice president of Shenzhen Hengyi Energy Technology Co., Ltd., delivered a keynote speech on "3.7V Lithium Polymer Battery Intelligent Manufacturing Back-end Processing Technology" at the meeting. The speech mainly focused on the overview of the 3.7V Lithium Polymer Battery back-end automatic line process, detailed description of the process segmentation, and technological innovation.

The following content is organized based on the on-site speech.

Hello everyone! My speech today is divided into three aspects. The first is an overview of the automatic line process of the back-end of lithium batteries, the second is a detailed description of the process segmentation, and the last is the technological innovation.

Overview of the automatic line of the back-end of 3.7V Lithium Polymer Battery production

The back-end of 3.7V Lithium Polymer Battery production mainly includes formation, OCV testing (shotting, spot welding, labeling or hot pressing, cutting gas bags, trimming, shaping, etc.), static, capacity division, grading, battery storage and other treatments. The processing process is connected through conveyors, elevators, RGV, stackers and other logistics equipment to achieve a complete and fully automatic solution.

Detailed description of process segmentation

First is the formation process. After the injection is completed, the active material is activated by charging with a small current; a solid electrolyte interface (SEI) film is generated on the surface of the carbon negative electrode; the characteristics of the SEI film are that it can cycle life, self-discharge, stability, safety and other characteristics; the factors that determine the SEI film are materials, formation environment temperature, formation current and voltage accuracy; the formation methods include negative pressure formation, open formation, normal temperature pressure formation, and high temperature pressure formation.

Secondly, let's talk about SEI. During the first charge and discharge process of liquid lithium-ion batteries, the electrode material reacts with the electrolyte to form a passivation layer covering the surface of the electrode material. The passivation layer is an interface layer with the characteristics of a solid electrolyte.

Its functions are: first, the electronic insulator is an excellent conductor of Li+, and Li+ can be freely embedded and removed through the passivation layer; second, the organic solvent is insoluble, preventing the co-embedding of solvent molecules, avoiding the damage to the electrode material caused by the co-embedding of solvent molecules, and greatly improving the cycle performance and service life of the electrode.

The characteristic of open-type formation is that the injection port is open, the advantages are simple equipment and low cost, and the disadvantage is that it is easy to enter water and impurities. Compared with open-type formation, the characteristic of negative pressure formation is that the negative pressure formation is vacuumed from the injection port. What are its advantages? It is a completely sealed environment with very sufficient gas discharge; the disadvantage is that the equipment is relatively complex and the cost is relatively high. The other is high-temperature formation and normal-temperature formation divided by temperature. High-temperature formation is completed at temperatures of 45 degrees, 60 degrees and 80 degrees. The purpose is to speed up the formation speed. The disadvantage is that the SEI film is loose and unstable. Normal temperature formation is completed at 20 degrees, 25 degrees, and 30 degrees. The advantage is that the SEI film is dense and stable, but the disadvantage is that the formation time is long. For high current formation, it is 0.5C, 1C, and 2C. The advantage is that the electrochemical reaction speed and SEI film growth speed are accelerated, and the formation time is shortened; the disadvantage is that the SEI film is loose, the consistency is poor, and it is unstable. Low current formation is 0.02C and 0.05C. Its advantages are that the SEI film is dense, consistent, and stable, but the disadvantage is that the formation time is long.

The main formation equipment includes high-precision power supply cabinets and automated needle beds. The high-precision power supply cabinet is a comprehensive charging and discharging mode that supports a variety of charging and discharging process combinations of 5V and 0-100A. The automated needle bed equipment is characterized by customization. The automated capacity needle bed equipment that meets customer needs adopts multi-contact technology to make sampling more stable and accurate, greatly saving the time of loading and unloading batteries and improving equipment utilization.

The third is the metal hard shell negative pressure formation process, which features imported professional negative pressure solutions, good air tightness, long service life, precise positioning of the mechanism, independent intellectual property rights and low probe contact impedance, dual-channel fire protection solutions with smoke exhaust and drainage systems, and dual monitoring of smoke and temperature. Another process is soft pack. The battery of the soft pack needs to use servo motor + sensor closed-loop control, and the pressure retention performance must be very good.

After the formation is completed, there is usually an NG sorting process below, and many manufacturers will use OCV testing.

Technological innovation

Speaking of technological innovation, Hengyi Energy has recently studied the latest technology, which is also a technology for small-scale application. At present, more than 1.5 charging and discharging cycles are required to complete a complete process in the constant volume process, and we use half of the charge and discharge cycle data to accurately reconstruct the complete charge and discharge curve, which can shorten the constant volume time by more than half.

Hengyi Energy has established a multi-parameter matching sorting system to solve the problem that a single parameter cannot fully reflect the quality of the battery, greatly increasing the consistency and accuracy of battery sorting.

At present, what is the pain point of the industry? It is the explosion or thermal runaway of the battery during the production process. Hengyi Neng has developed an effective thermal runaway warning and management system in half a year, that is, to make a main control in the whole system, from voltage to temperature tracking, to smoke alarm, protection, stacker, etc., to minimize possible accidents. This system may be launched on the market in about two months.

Finally, let me briefly introduce Hengyi Neng: Hengyi Neng was established in 2006. At present, Hengyi Neng has square, soft package, cylindrical back-end automatic production lines, as well as module and PACK automatic production lines. Welcome everyone to learn more.

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