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Abstract Volume swelling is a typical mode of battery failures, which happens not only in the operation but also during the storage of rechargeable batteries as a result of electrolyte degradation, particularly the chemical oxidation of electrolyte solvents by the active oxygen released in phase transition of the layered cathode materials. Aiming to remove the active oxygen, we herein propose Pyrite FeS 2 powder as an in-situ oxygen remover based on the fact that FeS 2 can be ultimately oxidized to Fe 2 O 3 and Li 2 SO 4 by the active oxygen, and the redox reaction depletes considerable amount of oxygen. By mixing FeS 2 powder into a conventional LiNi 0.80 Mn 0.10 Co 0.10 O 2 (NMC811) cathode, it is found that under normal cycling conditions of the Li/NMC811 cells, FeS 2 is electrochemically stable while being capable of reacting with active oxygen and hence stabilizing the cell's capacity retention. The concept proposed in this work provides a practically viable and cost-effective approach for preventing volume swelling of the rechargeable batteries based on the layered cathode materials. Graphical abstract Image 1 Highlights • Phase transition and oxygen release is an intrinsic nature of layered cathode materials. • Pyrite FeS 2 is proposed as an in-situ oxygen remover for rechargeable batteries. • In battery FeS 2 is electrochemically stable and capable of removing active oxygen. • FeS 2 suppresses impedance growth and the 2nd structure crack of layered cathode materials. [ABSTRACT FROM AUTHOR]

Abstract: In this communication, we disclose a proof-of-concept lithium/sulfur liquid battery that has exceptionally high capacity density. In such a battery, the cathode consists of a highly porous carbon cloth (CC) as the cathode current collector and a porous sulfur paper as the source of active material. In the first discharge, sulfur is reduced on the CC surface into high order lithium polysulfide (PS), which dissolves into liquid electrolyte and serves as the catholyte of the so-called “Li/S liquid battery”. By adopting a LiNO3-contained electrolyte to protect Li anode, the Li/S liquid cell is shown to cycle reversibly between 1.7 V and 2.8 V with an initial capacity of 778 mAh g−1 S, corresponding to a capacity density of 10.1 mAh cm−2 CC, which could be the highest capacity density among the rechargeable Li/S batteries reported ever. This work reveals that the high capacity density Li/S batteries can be made through a “Li/S liquid cell” by employing a highly porous carbon electrode to accommodate the insoluble sulfur reduction products (Li2S2/Li2S) with appropriate protection of the Li anode. [Copyright &y& Elsevier]