Despite extensive studies, the role of polar chemical interfaces on carrier materials anchoring polysulfide species remains an ambiguous but intriguing topic for lithium−sulfur batteries. Herein, to further investigate the effect of metal sulfides in the conversion of polysulfides, three kinds of M x S y (M = Cr, Mo, and W) are chosen and prepared in the forms of two-dimensional M x S y /C composites via a method using NaCl as a template and a subsequent high-temperature sulfuration process. Compared with a blank sample, the three composites exhibit superior adsorption of soluble polysulfides and faster kinetics of the deposition of Li 2 S 2 / Li 2 S, especially on Cr 3 S 4 /C and WS 2 /C. These differences in performances of the three composites are further evaluated by the values of the Gibbs free energy in each step of polysulfide conversion. In the conversion processes of Li 2 S 4 to Li 2 S 2 and then to Li 2 S, the values are more negative on Cr 3 S 4 and WS 2 , showing stronger promotion abilities for the formation of Li 2 S than MoS 2 . This work can effectively deepen the role of metal sulfides in the conversion process of polysulfides and provide valuable insights into the design of superior carriers for lithium−sulfur batteries.
While aqueous Zn-Na hybrid batteries have garnered widespread attentions because of its low cost and high safety, it is still challenging to achieve long cycle life and stable discharge voltage due to sluggish reaction kinetics, zinc dendrite formation, and side reactions. Herein, we design a Zn 2+ /Na + dual-salt battery, in which sodiation of the NVP cathode is favored against zinc intercalation under an energy threshold, leading to decoupled redox reactions on the cathode and anode. Systematic investigation of the electrolyte effects shows that the ion intercalation mechanism and kinetics in the triflate and acetate-based mixture electrolytes are superior to those in the common acetate-only electrolytes. As a result, we have achieved fast discharging capability, suppressed zinc dendrite, a stable discharge voltage at 1.45 V with small polarization, and nearly 100% Columbic efficiency in the dual-salt mixture electrolyte with optimized concentration of 1 M Zn(OAc)2 + 1 M NaCF3SO3. This work demonstrates the importance of electrolyte regulation in dual-salt hybrid batteries aqueous energy storage.
Understanding
of adsorption and kinetic conversion of polysulfide
lithium (LiPSs) in Li–S batteries is quite crucial for the
design of efficient effective sulfur carriers. Herein, based on the
possible interactions with LiPSs, Ce2O2S with
unique O–Ce–S bindings is proposed to be used as a promising
carrier additive and a 2D Ce2O2S/C composite
is synthesized via a one-facile NaCl-template method and subsequent
sulfuration under 700 °C. The 2D Ce2O2S/C
exhibits a stronger adsorption capability than CeO2/C through
the adsorption test for Li2S6. Combined with
XPS and DFT results, the superiority is mainly originated from the
formation of S–S and Li–S bonds between LiPSs and the
lattice S on the surface of Ce2O2S. The 2D Ce2O2S/C composite also exhibits a better catalytic
ability than CeO2 according to the change of the free energies
of the polysulfides during the discharge process, which coincides
with the lower oxidation potential for Li2S2/Li2S transition by cyclic voltammetry. Resultantly, the
cathodes using the Ce2O2S/C composite as a carrier
manifest an enhanced rate and cycling performances. Hence, our work
paves a phenomenon wherein Ce2O2S with O–Ce–S
bindings is more beneficial to improve the cycling stability of Li–S
batteries than CeO2 containing single Ce–O bonds,
which may be also suitable for other kinds of metallic sulfur oxide
compounds.
Liquid electrolyte determines the voltage window and extreme working temperature of supercapacitors. However, the effect of weak interaction between electrolyte species on voltage window and low-temperature capacitive performance is unclear. Herein, an electrolyte model system with increasing Hbond interaction was constructed to clarify this concern. The results indicated that strong H-bond interaction was positively correlated with the number of hydroxyls, which was beneficial to expand voltage window, but deteriorated rate performance; weak H-bond improved low-temperature performance. Supercapacitors with an optimized electrolyte presented high voltage and good low-temperature performance; even at À 40 °C, the maximum energy density could be maintained at 7.0 Wh kg À 1 (> 80 % retention relative to at À 20 °C). This study revealed the mechanism of the influence of the H-bonds on electrolyte voltage window and anti-freezing capability and provided a new insight for the design of electrolytes with both high working voltage and low-temperature performance.
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