| dc.description.abstract | Safety is the most sought-after property in Lithium battery. This research shows battery safety can be improved with the addition of functional additive to the cathode materials. In this research, barbituric acid (BTA) and its derivatives, 1,3DBTA(1,3-Dimethylbarbituric acid) which are well-known free radicals scavenger are first mixed with different organic copolymer (BMI, C4BMI, Si(MI)3, PMI) to form dendrimeric oligomers before compounded with various cathode materials which included LiCoO2, LiNiO2 and LiNi1/3Co1/3Mn1/3O2. LiCoO2 is the most widely used cathode material in present commercial lithium ion batteries.
SEM measurements confirmed the coating on the electrode materials is highly homogeneous, with part of the additive ingredient attached to PVdF binder. After formation with three repeating cycle, The SEI morphology was found to be smoother than pristine. Nitrogen mapping by EDS shows the dendrimeric additive is homogeneously spread out on the cathode materials surface which indicated the organic additives were adsorbed on the surface of LiNi1/3Co1/3Mn1/3O2. At 0.2C-rate and 6C-rate, the electrochemical performances of cathode containing additives were about 150 mAh/g and 105 mAh/g, respectively. Due to the additive effects, the lithium ion transfer rate are all decreased, and the SEI interface impedance rose. The delay of exothermic temperature and reduction of exothermic reaction heat release by more than 50% as derived from differential scanning thermal analyzer (DSC) suggested these additives effectively inhibits the reaction heat during oxygen release when temperature reached above 250℃ to 320℃. In cycle-life performance, oligomer with o-BMI and o-C4BMI retained 95.20% and 97.54% capacity at 50cycle under 0.2C-rate, but the pristine without any additive modification showed a capacity retention of 87% under the same condition.
Although the additives affect battery’s power density, carefully balancing the component composition, it is found the battery performance and security features can both be enhanced. Compared with other safety technology which uses flame retardants to reduce electrolyte flammability, temperature control is not satisfactory, and the charge capacity usually suffers greatly. In contrast, present approach improves both thermal stability and cycle life without much cost of the charge capacity.
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