Unraveling the Voltage Failure Mechanism in Metal Sulfide Anodes for Sodium Storage and Improving Their Long Cycle Life by Sulfur‐Doped Carbon Protection

Abstract

Metal sulfides are emerging as a promising anode material for sodium-ion batteries with high reversible capacities and fast reaction kinetics, but achieving long-cycling-life remains a great challenge. Here, taking cobalt sulfide as an example, its electrochemical sodium-ion storage failure phenomenon is first reported, which indicates that the battery cannot reach the cutoff voltage during charging. Detailed analyses demonstrate that such failure may originate from the dissolution and escape of polysulfide intermediates, further reacting with the released copper-ions from the current collector and inducing the occurrence of the shuttle effect. Based on the explored failure mechanism, a sulfur-doped carbon matrix with polar carbon sulfur bonds, which can firmly immobilize the dissolved polysulfides, is deliberately introduced into the Co 1−x S active particles (Co 1−x S/s-C) to improve their cycle stability. Consequently, the cycle life of the Co 1−x S/s-C anode for sodium-ion storage is extended from the original 125 to present 2000 cycles, even at high-rate current densities. Moreover, utilizing the carbon current collector instead of traditional copper can effectively delay the occurrence of the failure phenomenon. The present work promotes better fundamental understanding of the structural evolution of metal sulfide anodes during cycles, and the solution strategy can be extended to apply in other metal sulfides (ZnS, NiS).

Understanding electrolyte salt chemistry for advanced potassium storage performances of transition‐metal sulfides

“…Using KFSI/EC + DEC as an example, the representative force responses basically consist of two stages (Figure 5C), including (i) a linear force-increasing region, indicating an elastic process, and (ii) a quasi-constant force region, corresponding to an ideal plastic process or a yielding process. 55 These results are in line with the force response of elastomers. In contrast, the force responses of the electrode cycled in KPF 6 /EC + DEC are totally different (Figure 5D).…”

Engineering Pocket‐Like Graphene–Shell Encapsulated FeS2: Inhibiting Polysulfides Shuttle Effect in Potassium‐Ion Batteries

“…At the same time, FeS 2 @NS‐3DHCs are more uneven and rougher than FeS 2 @G@NS‐3DHCs, which hints that Cu has reacted with potassium polysulfides originated from the electrode material. [ 34 ] The elemental mappings of SEM of two cycled electrode materials display the uniform presence of numerous Cu elementals (Figure S9d,e, Supporting Information). However, the Cu content of FeS 2 @NS‐3DHCs electrode material is around five times that of FeS 2 @G@NS‐3DHCs, which suggests that Cu has involved in the charging/discharging, and the phenomenon is more serious when FeS 2 @NS‐3DHCs act as an anode electrode for PIBs.…”

“…[ 33 ] In addition, Wang and co‐workers immobilized the dissolved polysulfides via polar carbon–sulfur bonds, thus achieving a stable cycle of 2000 cycles at 5 A g −1 in sodium‐ion batteries. [ 34 ] Obviously, the strong adsorption ability for polysulfides has become the key to inhibiting the shuttle effect of polysulfides. Yet, there is still a lack of in‐depth research to clarify the interaction between FeS 2 and protective shell in the ether‐based electrolyte.…”

Enhancing the Electrochemical Performance of Sodium‐Ion Batteries by Building Optimized NiS2/NiSe2 Heterostructures

“…[24,37,38] A pair of redox peaks near 0.01 V might be attributed to the pseudo-capacitive process at the interface of the formed nanoparticles. [39] In the second cycle, the cathodic peaks at ≈1.24 and 0.9 V shift positively to ≈1.58 and 1.01 V, and the anodic peaks at ≈1.89 and 2.1 V shift negatively to ≈1.82 and 1.96 V, which are caused by the enhanced electrochemical kinetics of electrode after the first cycle owing to the formation optimized material structure. The profiles of subsequent cycles remained steady and overlapped well, indicating that the electrochemical reaction was reversible and stable.…”