Blocking Polysulfide with Co2B@CNT via “Synergetic Adsorptive Effect” toward Ultrahigh-Rate Capability and Robust Lithium–Sulfur Battery

• Published in: ACS nano 2019-06, Vol.13 (6), p.6742-6750
• Main Authors: Guan, Bin, Zhang, Yu, Fan, Lishuang, Wu, Xian, Wang, Maoxu, Qiu, Yue, Zhang, Naiqing, Sun, Kening
• Format: Article
• Language: English
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.9b01329

Li–S batteries have attracted great interest as the next-generation secondary batteries due to their high energy density, being environmentally friendly, and low price. However, the road to commercialization of lithium–sulfur batteries remains limited owing to the “shuttle effect” of soluble polysulfides, which results in the inferior cycle stability. Herein, a potent functional separator is developed to restrain the “shuttle effect” by coating Co2B@carbon nanotube layer on the commercialized polypropylene separator. In merits of the coadsorption of Co sites and B sites, such Co2B shows highly efficient polysulfides block (11.67 mg/m2 for Li2S6). Besides, the composite also exhibits obviously catalysis from Li2S8 to Li2S. By combining the fast electron transportation along the carbon nanotube, a superior rate performance is achieved with the modified separator and common carbon–sulfur cathode. Typically, the cell with Co2B@CNT shows prominent cycling life with a capacity degradation of 0.0072% per cycle (3000 cycles) and ultrahigh-rate capability at 5 C current (1172.8 mAh/g), which outstands the previously reported polysulfides barrier layer. The cell with Co2B@CNT can exhibit electrochemical performance at areal capacity of 5.5 mAh/cm2 (0.5 C) when the sulfur loading increased to 5.8 mg/cm2. This work defines an efficacious strategy to restrain the “shuttle effect” of polysulfides and shed light on the great potential of borides in Li–S battery.