Combination Technology for Safer Design of Lithium-Ion Batteries

For further penetration of lithium-ion battery, safer battery design with high energy density is required. In the case of the thermal runaway of conventional lithium-ion batteries, the reaction of electrolyte on the surface of graphite anode at higher temperature causes the gas generation with the temperature rise. Subsequently, the short circuit due to the separator meltdown leads to the oxygen release by the pyrolysis of cathode and the thermite reaction above the melting of aluminum utilized for the current collector and the cell package. The construction of novel safer battery systems with high energy density is possible through a judicious choice of each component: cathode material, electrolyte, separator, anode material, current collector and package. We develop safer battery configurations through the analysis of practical batteries using various techniques such as calorimetry and overcharge / internal short-circuit tests. In this study, we assemble 1 Ah class pouch-type full cell with lithium iron phosphate cathode and silicon oxide anode [1]. The full cell shows good charge-discharge properties even at high-rate and 100˚C (Figure 1). On the estimation, however, the electrochemical energy of both electrode active materials is only about 3% of the total thermal energy of full cell. Thus, we replace aluminum with stainless steel utilized for the current collector and package. In addition, we select a separator of heat-stable nonwoven fabric instead of polyethylene/polypropylene. The total thermal energy of full cell by the alternative separator, current collector and package is found to be reduced to 14% of the initial value. In short-circuit testing, the full cell did not show fire though heat and smoke were generated since the maximum temperature of the cell is only 52˚C. In this way, it is possible to design batteries with highly safe by considering the non-flammability of each component such as the current collector and the package as well as the separator. References [1] M. Yanagida, T. Mukai, Y. Ikeuchi, N. Yamashita, T. Sakamoto, H. Senoh and H. Tanaka, Abstract of the 60th Battery Symposium in Japan, 2B23 (2019). Figure 1