Fabrication of layered Ti<sub>3</sub>C<sub>2</sub> with an accordion-like structure as a potential cathode material for high performance lithium–sulfur batteries

765

434

Ti C T , a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti C T directly influence its electrochemical performance, e.g., the use of a well-designed 2D Ti C T as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion-diffusion lengths, and improved in-plane carrier/charge-transport kinetics. Some recent progresses of Ti C T MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti C T MXene including supercapacitors, lithium-ion batteries, sodium-ion batteries, and lithium-sulfur batteries. The current opportunities and future challenges of Ti C T MXene are addressed for energy-storage devices. This Review seeks to provide a rational and in-depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti C T , which will promote the further development of 2D MXenes in energy-storage applications.

Section: Potential Applicationsmentioning

confidence: 95%

Section: Potential Applicationsmentioning

confidence: 99%

Recent Advances in Layered Ti₃C₂T_x MXene for Electrochemical Energy Storage

Xiong

Bai

et al. 2018

765

434

“…We highlight the following superiorities of our TiO 2 QDs@MXene nanohybrids over neat MXene nanosheets as a sulfur host: First of all, TiO 2 QDs are uniformly decorated on MXene nanosheets, acting as spacers to prevent them from restacking and preserve their 2D geometry. The well‐preserved 2D geometry therefore guarantees larger electrode–electrolyte contact area and higher sulfur loading . Second, the stronger adsorption energy of polysulfides with TiO 2 than with Ti 3 C 2 T x (which is weakened by the surface functional groups) is essential for better on‐site polysulfide retention, and helps to reduce the polarization of the sulfur cathode especially at high rates .…”

mentioning

confidence: 99%

Ultrathin MXene Nanosheets Decorated with TiO₂ Quantum Dots as an Efficient Sulfur Host toward Fast and Stable Li–S Batteries

Gao

Xie

Zhu

et al. 2018

130

Being conductive and flexible, 2D transition metal nitrides and carbides (MXenes) can serve in Li-S batteries as sulfur hosts to increase the conductivity and alleviate the volume expansion. However, the surface functional groups, such as OH and F, weaken the ability of bare MXenes in the chemisorption of polysulfides. Besides, they create numerous hydrogen bonds which make MXenes liable to restack, resulting in substantial loss of active area and, thus, inaccessibility of ions and electrolyte. Herein, a facile, one-step strategy is developed for the growth of TiO quantum dots (QDs) on ultrathin MXene (Ti C T ) nanosheets by cetyltrimethylammonium bromide-assisted solvothermal synthesis. These QDs act as spacers to isolate the MXene nanosheets from restacking, and preserve their 2D geometry which guarantees larger electrode-electrolyte contact area and higher sulfur loading. The stronger adsorption energy of polysulfides with TiO (than with Ti C T ), as proven by density functional theory calculations, is essential for better on-site polysulfide retention. The ultrathin nature and protected conductivity ensure rapid ion and electron diffusion, and the excellent flexibility maintains high mechanical integrity. In result, the TiO QDs@MXene/S cathode exhibits significantly improved long-term cyclability and rate capability, disclosing a new opportunity toward fast and stable Li-S batteries.

“…As expected, when acting as a sulfur host, the sulfur cathode delivered high capacity and superior cycling stability, even with 70 wt% S (Figure d). Other metal carbides, such as MXene Ti 3 C 2 , TiC, and Fe 3 C with similar characteristics, have also been investigated as the sulfur host in Li–S batteries.…”

Section: Other Non‐carbon Sulfur Hosts For Li–s Batteries (Metal Hydrmentioning

confidence: 99%

Novel Non‐Carbon Sulfur Hosts Based on Strong Chemisorption for Lithium–Sulfur Batteries

Zhu

Wang

Miao

et al. 2018

Lithium-sulfur (Li-S) batteries are considered as promising candidates for energy storage systems owing to their high theoretical capacity and high energy density. The application of Li-S batteries is hindered by several obstacles, however, including the shuttle effect, poor electrical conductivity, and the severe volume expansion of sulfur. The traditional method is to integrate sulfur with carbon materials. But the interaction between polysulfide intermediates and carbon is only weak physical adsorption, which easily leads to the escape of species from the framework (shuttle effect) of the material causing capacity loss. Recently, however, there has been a trend for the introduction of novel non-carbon materials as sulfur hosts based on the strong chemisorption. This review highlights recent research progress on novel non-carbon sulfur hosts based on strong chemisorption, in Li-S batteries. In comparison with carbon-based sulfur hosts, most non-carbon sulfur hosts have been demonstrated to be polar host materials that could efficiently adsorb polysulfide via strong chemisorption, mitigating their dissolution. The intrinsic mechanism associated with the role of non-carbon-based host materials in improving the performance of Li-S batteries is discussed.