5 years ago

Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility [Chemistry]

Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility [Chemistry]
Chunsheng Wang, Fei Wang, Xiulin Fan, Kang Xu, Oleg Borodin, Wei Sun, Zhaohui Ma, Tao Gao, Khalil Amine, Chongyin Yang, Singyuk Hou, Liumin Suo

Leveraging the most recent success in expanding the electrochemical stability window of aqueous electrolytes, in this work we create a unique Li-ion/sulfur chemistry of both high energy density and safety. We show that in the superconcentrated aqueous electrolyte, lithiation of sulfur experiences phase change from a high-order polysulfide to low-order polysulfides through solid–liquid two-phase reaction pathway, where the liquid polysulfide phase in the sulfide electrode is thermodynamically phase-separated from the superconcentrated aqueous electrolyte. The sulfur with solid–liquid two-phase exhibits a reversible capacity of 1,327 mAh/(g of S), along with fast reaction kinetics and negligible polysulfide dissolution. By coupling a sulfur anode with different Li-ion cathode materials, the aqueous Li-ion/sulfur full cell delivers record-high energy densities up to 200 Wh/(kg of total electrode mass) for >1,000 cycles at ∼100% coulombic efficiency. These performances already approach that of commercial lithium-ion batteries (LIBs) using a nonaqueous electrolyte, along with intrinsic safety not possessed by the latter. The excellent performance of this aqueous battery chemistry significantly promotes the practical possibility of aqueous LIBs in large-format applications.

Publisher URL: http://www.pnas.org/content/114/24/6197.short

DOI: 10.1073/pnas.1703937114

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