Zhang Hui, Zou Mingchu, Zhao Wenqi, Wang Yunsong, Chen Yijun, Wu Yizeng, Dai Linxiu, Cao Anyuan
Department of Materials Science and Engineering, College of Engineering , Peking University , Beijing 100871 , China.
Center for Composite Materials and Structures , Harbin Institute of Technology , Harbin 150080 , China.
ACS Nano. 2019 Apr 23;13(4):3982-3991. doi: 10.1021/acsnano.8b07843. Epub 2019 Mar 22.
Lithium-sulfur (Li-S) batteries are next-generation energy storage systems with high energy density, and the rate performance is a very important consideration for practical applications. Recent approaches such as introducing catalytic materials to facilitate polysulfide conversion have been explored, yet the results remain unsatisfactory. Here, we present an optimized Li-S electrode featured by a large amount of highly dispersed CoS nanoparticles (∼10 nm in size) throughout a hierarchical carbon nanostructure hybridized from ZIF-67 and carbon nanotube (CNT) sponge. This enables homogeneous distribution and close contact between infiltrated sulfur and CoS nanoparticles within the ZIF-67-derived N-doped carbon nanocubes, leading to effective chemical interaction with polysulfides, maximum catalytic effect and enhanced lithium ion diffusion, while the built-in three-dimensional CNT network ensures high electrical conductivity of the electrode. As a consequence, the Li-S battery exhibits both extraordinary rate performance by maintaining a capacity of ∼850 mAh g at very high charge/discharge rate (5 C) and long-term cycling stability with 85% retention after 1000 cycles at 5 C (an average capacity fading rate of only 0.0137% per cycle).
锂硫（Li-S）电池是具有高能量密度的下一代储能系统，倍率性能是实际应用中非常重要的考量因素。近期人们探索了诸如引入催化材料以促进多硫化物转化等方法，但结果仍不尽人意。在此，我们展示了一种优化的锂硫电极，其特征在于大量高度分散的硫化钴纳米颗粒（尺寸约为10纳米）遍布由ZIF-67和碳纳米管（CNT）海绵杂化而成的分级碳纳米结构。这使得渗透的硫与ZIF-67衍生的氮掺杂碳纳米立方体内的硫化钴纳米颗粒能够均匀分布并紧密接触，从而与多硫化物产生有效的化学相互作用，实现最大催化效果并增强锂离子扩散，同时内置的三维碳纳米管网络确保了电极的高导电性。因此，该锂硫电池既展现出非凡的倍率性能，在非常高的充放电速率（5C）下保持约850 mAh g的容量，又具有长期循环稳定性，在5C下1000次循环后保持85%的容量保持率（平均每次循环容量衰减率仅为0.0137%）。
