Non-Negligible Role of Multifunctional MXene Hosts for Li–S Batteries: Anchoring and Electrocatalysis

Abstract

Lithium−sulfur (Li−S) batteries have attracted great enthusiasm in recent years. Nevertheless, the serious shuttle effect of lithium polysulfides (Li 2 S n ), poor conductivity of S and intermediate products, and relatively slow dynamics make its commercial application face severe challenges. Here, functionalized M 2 CT 2 MXenes (M = Ti, Nb, Cr; T = bare, O, F, OH) were used as the sulfur host to build multifunctional cathodes, in which the inhibition of the shuttle effect by the anchoring effect and accelerating discharging/charging kinetics by electrocatalysis were studied via first-principles. The strong anchoring strength of M 2 CO 2 /M 2 CF 2 to Li 2 S n could effectively suppress the shuttle behavior. The anchoring ability of MXenes is a double-edged sword, and moderate anchoring strength should be considered. Compared comprehensively, Nb 2 CO 2 has a better electrocatalysis performance for the sulfur reduction reaction during discharging. It also accelerates the decomposition of Li 2 S and migration of Li + on the cathode which increases charging kinetics. The improvement in kinetics is related to the enhancement of electronic conductivities of Nb 2 CO 2 −Li 2 S n composites. In short, Nb 2 CO 2 -based multifunctional sulfur cathodes effectively suppress the shuttle effect and improve reaction kinetics. This work expands the application of the MXene family, especially providing guidelines for the utilization of Nb-based MXene in energy storage.

Rational design of MXene-based single atom catalysts for Na–Se batteries from sabatier principle

“…It is worth noting that the O groups of Ti 2 CO 2 /Nb 2 CO 2 are located on the M2 site, while the O groups of Cr 2 CO 2 prefer to locate on the C site, as previously reported in our work. 15 Zn-M 2 CO 2 was constructed on the pristine MXenes models (Fig. 2a).…”

“…The metal atom orbitals (Ti-3d, Cr-3d, and Nb-4d) contribute the majority of their metallicity. In the case 15 where MXenes with a smaller lattice constant always have a stronger anchoring ability. Besides this, a wider DOS around the E Fermi level always leads to an increase in the energy levels of the valence band, which is beneficial for the excitation of electrons in MXene.…”

First-principles study on the structure and electronic properties of M2CSx (M = Sc, Ti, Y, Zr and Hf, x = 1, 2)

“…24 Superconductivity was rst observed in Nb 2 CT x terminated with S, Se, or NH groups, while no superconducting transition was found for bare and O-terminated Nb 2 C. 16 Some M 2 CT 2 (T = O, OH or S)-based multifunctional sulfur cathodes were found to effectively suppress the shuttling effect and exhibit excellent cycle performance and high specic capacity in lithium-sulfur batteries. [25][26][27] Zhu et al showed the O, OH and F groups on Zr 2 CT x can be seemingly exchanged with S groups through the proposed reaction in CS 2 solution. 28 A number of Sfunctionalized MXenes have been reported as electrode materials for potential metal ion batteries due to their lower diffusion barrier and higher storage capacity.…”

Tri(ethylene glycol) modified HYC‐100 resin for lithium ion recovery from aqueous solution

“…Their adsorption capacities are not satisfactory with the capacity less than 7 mg/L 10 . Polymeric resin have been well‐developed for wide application for water purification, metal ion adsorption and medical waste treatment, and so forth 11–17 . Although the crown ethers have been recognized as excellent binding units for alkali metal ion, its toxicity and high costs prevent direct modification on the polymeric resin to enhance the adsorption performance 18–27 .…”