期刊
ADVANCED ENERGY MATERIALS
卷 12, 期 1, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.202102774
关键词
capacity fading mechanism; cathode electrolyte interface; lithium-sulfur batteries; solid-phase conversion
类别
资金
- National Key R&D Program of China [2018YFB0905400]
- National Natural Science Foundation of China [51972131, 51632001]
The integrity of CEI is closely related to the sulfur content and electrolyte amount. When the volume of reduction product exceeds the maximal volume of the carbon host, the as-formed CEI is unable to withstand the volume variation upon repeated lithiation/delithiation, leading to decreased cycle stability.
The cathode electrolyte interface (CEI) formed on the surface of the sulfur cathode plays a vital role in determining whether lithium-sulfur batteries can function through a solid-phase conversion reaction, which can effectively hinder the dissolution of polysulfides. However, there is still a lack of systematical research on the evolution and failure mechanism of the CEI for Li-S batteries. Here, it is found that the integrity of the as-formed CEI is strongly related to the content of sulfur and the amount of electrolyte. When the volume of reduction product (Li2S/Li2S2) exceeds the maximal volume of the carbon host, the as-formed CEI is unable to withstand the volume variation upon repeated lithiation/delithiation. The repeated fracture and repair of CEI unceasingly consumes electrolyte and active materials. Thus, to achieve prolonged cycle stability via solid-phase conversion, the content of sulfur and the interior space of the host should be well matched. Based on the above understanding, the designed sulfur-graphite full cell shows an excellent cyclability over 2000 cycles. This work reveals the failure mechanism of solid-phase conversion reactions in Li-S batteries, and provides some inspiration for designing long-life and high-sulfur-content cathode materials.
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