Artificial Solid Electrolyte Interface Enhances Lithium Battery Life Cycle and Safety

• Main Authors: Wan-Tzu Lo, 羅婉慈
• Other Authors: Po-Jen Chu
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/eyxe9w

碩士 === 國立中央大學 === 化學學系 === 105 === This study disclosed a novel approach to improve lithium battery life cycle which also eliminated thermal run-away. The formation of artificial solid electrolyte interface (SEI) coating (achieved by several effective approaches) was shown to improve lithium battery cyclic performance at elevated temperature, high rate charge/discharge performance, and mostly avoided thermal run-away. These artificial solid electrolyte modifications with different degree of pore densities are found to exhibit different effects on lithium-ion cell performances using EC: DMC: EMC+VC+ LiPF6-based electrolyte. The study shows the pre-formed solid electrolyte interface on both anode (MCMB) and cathode (NMC=1:1:1), changed the SEI compositions with improved electrochemical stability, that consumes less carbonates and hindered salt decomposition, generates much less HF. The interface composition and structure after pre-formation and after cycling in coin cell is investigated via scanning electron microscope (SEM), electrochemistry impedance spectroscopy (EIS) and cyclic voltammetry (CV) test using both Li(Ni1/3Mn1/3Co1/3)O2/Li half-cell and Li/graphite half-cell. The chemical stability under elevated temperature is characterized by nuclear magnetic resonance (NMR). We found that this additive formed more stable solid electrolyte interface (SEI) on electrodes during charge and discharge operation, and has prevented electrolyte and lithium salts from decomposition under high temperature operation conditions. Two types of Artificial SEI modifications bearing denser and harder SEI modifications (HPKS) and softer and more elastic SEI modifications (BPMI) are compared. After 80th cycling at room temperature, the capacity retention is found to be 88.2% with VC (vinylene carbonate), 94.5% with HPKS Artificial SEI, and about 96.5% with BPMI Artificial SEI. After 30th cycling at 60oC, the capacity retention is found to be 93.0% with VC Artificial SEI, 97.4% with HPKS Artificial SEI, and about 95.1% with BPMI Artificial SEI.