Study On The Process Of Laboratory Fabrication And Test System For Lithium-ion Batteries

The fabrication and test system suitable for the laboratory lithium-ion battery rapid evaluation was developed on the basis of research achievements of lithium-ion battery and materials in Institute of Power Source & Ecomaterials Science, Hebei University of Technology. The slurry preparation and electrode piece rolling process of laboratory lithium-ion battery were also systematically investigated in this paper.The fabrication and test system of laboratory lithium-ion battery, including high-speed slurry dispersion system, small-scale coating system, soft-package 18650/14500 cell technology, microclimate controlling technology and electrochemical testing system, was developed. Revolution eccentric mixing system with constant-temperature water circulation was designed to improve the slurry quality and shorten the slurry preparation time. Coating thickness regulating element was improved to enhance the control accuracy of coating thickness. Electrode piece rolling equipment with large diameter roller and small stand structure was developed, which is convenient for display and operation in laboratory, and simultaneously could eliminate the divergent stripes of rolled electrode piece. Soft-package cylindrical lithium-ion battery sealing system, which is convenient for battery testing and disassembly analysis, was developed. The temperature-adjust–able electrochemical testing system is also designed, which is suitable for battery performance testing under different temperatures with convenient operation. This fabrication and test system has the merits of small size, low price and good reproducibility, very suitable for the verification and evaluation of lithium-ion battery and materials in laboratory.Based on the above system, the LiFePO4 slurry preparation technology of laboratory lithium-ion battery was systematically investigated in this paper. The effects of stirring speed, feeding ways and gel concentration in the slurry preparation process on the stability and dispersion of slurry, coating adhesion and electrochemical performance of battery were intensively investigated. The results showed that the optimal slurry preparation parameters were that at room temperature, several times feeding ways, stirring speed 2000 rpm and gel concentration 6%. The as-obtained 14500 soft package LiFePO4 battery exhibited an initial discharge capacity of 508.1 mAh, initial discharge efficiency of 86%, with a cycling retention rate of 99.5% after 100 cycles at 1C rate.The LiFePO4 cathode electrode rolling process of laboratory lithium-ion battery was also optimized. The effects of roller spacing and compaction density on the electrode thickness rebounding rate, internal resistance and electrochemical performance of battery were intensively investigated. The results showed that the optimal rolling process parameters were the roller spacing of 60-70μm and compaction density of 2.28g/m2. The qualified electrode could be obtained through less roller times by the optimum process, without death marks, stripes and bright surface. The as-obtained battery also exhibited excellent electrochemical performance.