In Situ Observation and Electrochemical Study of Encapsulated Sulfur Nanoparticles by MoS₂ Flakes

Abstract

Sulfur is an attractive cathode material for next-generation lithium batteries due to its high theoretical capacity and low cost. However, dissolution of its lithiated product (lithium polysulfides) into the electrolyte limits the practical application of lithium sulfur batteries. Here we demonstrate that sulfur particles can be hermetically encapsulated by leveraging on the unique properties of two-dimensional materials such as molybdenum disulfide (MoS). The high flexibility and strong van der Waals force in MoS nanoflakes allows effective encapsulation of the sulfur particles and prevent its sublimation during in situ TEM studies. We observe that the lithium diffusivities in the encapsulated sulfur particles are in the order of 10 m s. Composite electrodes made from the MoS-encapsulated sulfur spheres show outstanding electrochemical performance, with an initial capacity of 1660 mAh g and long cycle life of more than 1000 cycles.

Rational Fabrication of Nitrogen and Sulfur Codoped Carbon Nanotubes/MoS2 for High‐Performance Lithium–Sulfur Batteries

“…In general, during the discharge/charge process, the soluble long‐chain LiPSs can move between the cathode and anode; therefore, a fast conversion of sulfur species may be conducive to preventing the dissolution of polysulfides and restraining the polysulfide shuttle effect, to some extent . Particularly, molybdenum sulfide (MoS 2 ), as a representative 2D layered transition‐metal sulfide, possesses high electrochemical activity, a unique three‐atom‐layer (S–Mo–S) structure, and outstanding chemical stability . Furthermore, MoS 2 is a cost‐effective and robust catalyst, which has displayed a highly effective catalytic effect in several important reactions including the oxygen evolution reaction, oxygen reduction reaction, and hydrogen evolution reaction .…”

In Situ Formed Protective Barrier Enabled by Sulfur@Titanium Carbide (MXene) Ink for Achieving High‐Capacity, Long Lifetime Li‐S Batteries

“…Among various sulfur hosts, such as TiC@graphene,57 graphene‐poly(ethylene glycol),25 graphene/VO 2 ,29 CNTs,24 MoS 2 ,61 and MXenes (Ti 2 CT x and Ti 3 C 2 T x ‐CNT),44, 46 our S@Ti 3 C 2 T x electrode demonstrates the lowest capacity decay rate. We believe several factors could be responsible for the excellent electrochemical performance: (1) The crosslinked network ensures rapid electron transport and ion diffusion kinetics; (2) The S NPs intimately decorate the conductive Ti 3 C 2 T x mediator, allowing improved S utilization and reversible redox reactions; (3) The polar host facilitates the direct nucleation of Li 2 S and suppresses the polysulfides shuttle.…”

In Situ Techniques for Developing Robust Li–S Batteries

“…Volume‐expansion information obtained by in situ TEM not only yields critical information about the structural stability of the electrode, but also provides insights into the prevention of LPS formation. Tang et al developed a sulfur electrode encompassing a MoS 2 ‐encapsulated hollow sulfur sphere composite. A high initial capacity of 1660 mA g −1 can be achieved at 0.1C (1.5 mg cm −2 sulfur loading).…”

“…For example, the volume expansion of LSB active materials was reported through in situ TEM studies in the early years, but was simply used to justify the structural instabilities/stabilities of the target electrodes. However, Tang recently managed to correlate this basic observation to Li + diffusion kinetics, which in turn provides solid evidence of LPS dissolution restriction.…”