나노 카본을 이용한 3D 구조 황 양극 및 분리막을 사용하는 고 에너지 밀도 유연 리튬-황 배터리

Abstract

For the realization of next-generation foldable and wearable electronic products, it is essential to develop high-performance and mechanically flexible batteries at the industry level. Lithium-sulfur(Li–S) batteries are a promising alternative to conventional lithium-ion batteries owing to their high theoretical capacity (1675 mAh g-1) and natural abundance. However, their widespread adoption is hampered by practical concerns such as their rigid form factor, limited cycle stability, and flammability under mechanical failure. Herein, we report flexible and high-energy density Li–S batteries based on fibrous flexible sulfur cathodes and separators functionalized by carbon nanotubes (CNT). [1,3] The cellulose nanofiber (CNF)-based sulfur cathodes were fabricated by deposing sulfur on the surface of multi-walled CNTs and mixing with single-walled CNTs to increase the electrical conductivity of sulfur electrode and to form a three-dimensional porous structure to conduct ions electrode without the use of a metal collector.[27,30] Glass fiber separator was coated with CNTs via a cost-effective method to suppress the shuttle effects by adsorbing Lithium–polysulfide in carbon materials with the small pores, thereby improving the redox kinetics and cycle stability. The fabricated Li–S batteries showed the high capacities ranging from 940 to 597mAh g-1 as the charge current density ranged from 1.57 to 15.74 mAh cm-2 at 25 ℃, and the coulombic efficiency exceeding 90 % even after 50 charge/discharge cycles. With its structural uniqueness and chemical functionality, the Li–S batteries are mechanically flexible and rollable without any damage. Under bending states, those cells exhibited a high first discharge capacity of 834 mAh g-1 and maintained a remarkable capacity of 754 mAh g-1 at a current density of 1.06 mAh cm-2 over 100 charge/discharge cycles.