Abstract

The lithium-ion battery is subject to the limited theoretical specific capacity of electrode materials, which is difficult to achieve capacity breakthrough. However, the theoretical specific capacity of the sulfur cathode for lithium-sulfur battery is 1675 mAh g⁻¹ and the energy density is 2600 Wh kg⁻¹. However, lithium-sulfur batteries suffer from three problems: “shuttle effect,” sulfur electron/ion insulation, and volume expansion. Moreover, the carbon materials or metal sulfides alone cannot achieve the dual effects of excellent conductivity and chemisorption as sulfur carriers. Therefore, 350 nm and 1 μm of polyhedron with mesoporous carbon and Co₃S₄ were prepared (denoted as C/Co₃S₄@S (S) for the small one and C/Co₃S₄@S (L) for the large one, respectively) using PVP modified self-assembled Co-MOFs as a sacrificial template. The C/Co₃S₄ (S) carrier provided a sulfur-filled channel, and shortened the electron transport path with excellent conductivity. Simultaneously, the polar Co₃S₄ chemisorption of polysulfide and hollow structure provided a sufficient storage for sulfur. As the cathode of lithium-sulfur battery, C/Co₃S₄@S (S) exhibited an initial capacity of 1153 mAh g⁻¹ at 0.5 C, and the capacity decay rate per cycle is only 0.057% during 500 cycles at 1 C, compared to 1 μm C/Co₃S₄@S (L) efficiently improved the cycle stability.

摘要

锂离子电池受制于电极材料的理论比容量有限，难以实现容量突破。然而，锂硫电池硫正极的理论比容量为1675 mAh g ^-1，能量密度为2600 Wh kg ^-1。然而，锂硫电池存在三个问题：“穿梭效应”、硫电子/离子绝缘和体积膨胀。此外，碳材料或金属硫化物单独作为硫载体无法实现优异的导电性和化学吸附的双重效果。_{因此，制备了具有介孔碳和 Co 3} S ₄的350 nm 和 1 μm 多面体（记为 C/Co ₃ S ₄@S (S) 代表小号，C/Co ₃ S ₄ @S (L) 代表大号）使用 PVP 改性自组装 Co-MOFs 作为牺牲模板。C/Co ₃ S ₄ (S)载体提供了硫填充的通道，缩短了电子传输路径，具有优异的导电性。同时，多硫化物的极性Co ₃ S ₄化学吸附和中空结构为硫提供了足够的储存。作为锂硫电池的正极，C/Co ₃ S ₄ @S (S) 在0.5 C时的初始容量为1153 mAh g ^-1，在1 500次循环中每个循环的容量衰减率仅为0.057% C，与 1 μm C/Co 相比₃ S ₄ @S (L) 有效地提高了循环稳定性。