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고성능 리튬-황 전지를 위한 금속산화물을 첨가한 탄소나노튜브 프리스탠딩 전극
신윤정,정현서,김은미,김태윤,정상문,Yun Jung Shin,Hyeon Seo Jeong,Eun Mi Kim,Tae Yun Kim,Sang Mun Jeong 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3
Lithium-sulfur batteries, recently attracting attention as next-generation batteries, have high energy density but are limited in application due to sulfur's insulating properties, shuttle phenomenon, and volume expansion. This study used an economical and simple vacuum filtration method to prepare a freestanding electrode without a binder and collector. Carbon nanotubes (CNTs) are used to improve the electrical conductivity of sulfur, where CNT also acts as both collector and conductor. In addition, metal oxides (MO<sub>x</sub>, M=Ni, Mg), which are easy to adsorb lithium polysulfide, are added to the CNT/S electrode to suppress the shuttle reaction in lithium-sulfur batteries, which is a result of suppressing the loss of active sulfur material due to the excellent adsorption of lithium polysulfide by metal oxides. The MO<sub>x</sub>@CNT/S electrode exhibited higher capacity characteristics and cycle stability than the CNT/S electrode without metal oxides. Among the MO<sub>x</sub>@CNT/S electrodes, the NiO@CNT/S electrode displayed a high discharge capacity of 780 mAh g<sup>-1</sup> at 1 C and an extreme capacity decrease to 134 mAh g<sup>-1</sup> after 200 cycles. Although the MgO@CNT/S electrode exhibited a low discharge rate of 544 mAh g<sup>-1</sup> in the initial cycle, it showed good cycle stability with 90% of capacity retention up to 200 cycles. Further, to achieve high capacity and cycle stability, the Ni<sub>0.7</sub>Mg<sub>0.3</sub>O@CNT/S electrode, mixed with Ni:Mg in the ratio of 0.7:0.3, manifested an initial discharge rate of 755 mAh g<sup>-1</sup> (1 C) and a capacity retention rate of more than 90% after 200 cycles. Therefore, applying binary metal oxides to CNT/S provides a freestanding electrode for developing economical and high-performance Li-S batteries, effectively improving lithium polysulfide's high capacity characteristics and dissolution.