Dual functional effect of the ferroelectricity embedded interlayer in lithium sulfur battery

초록

A carbon nanotube sheet having homogeneously distributed BaTiO3 is applied to the Li-S cell system as a pseudo current collector between the cathode and separator. This interlayer serves as a site distributor, where poly sulfide eluted from the cathode continuously reacts, and it is expected to play a role as a more effective current collector by mixing the ferroelectric material. A cell utilizing a ferroelectricity embedded interlayer exhibits a higher capacity (908 mAh g(-1)) at 0.2C than that of carbon alone (740 mAh g(-1)) at 200th cycle. This result corresponds to a capacity retention ratio enhancement from 67.5% to 75.6%. Furthermore, it is confirmed that the retention of the coulombic efficiency is effectively maintained in long cycles at 0.5C (94.5%-99.6%). This is not only because the modified interlayer functions as an effective current collector owing to the high affinity of the ferroelectric material to polysulfide, but also because ferroelectricity in the interlayer acts as a polysulfide anchor. The evenly distributed polarization leads to a uniform deposition of sulfur, which results in the prevention of inactive sulfur agglomeration and dissolution of polysulfide. Thus, the utilization of active material can be improved with stabilized reaction.

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