Macro/Mesoporous Carbon/Defective TiO₂ Composite as a Functional Host for Lithium–Sulfur Batteries

Abstract

Lithium–sulfur batteries (LSBs) hold great potential as next-generation electrochemical energy storage and conversion systems owing to their higher theoretical capacity (1675 mAh/g). However, the shuttling of soluble polysulfides with slow redox reaction kinetics has restricted the commercialization of LSBs. The design and synthesis of effective cathode hosts provide a promising solution to improving the electrochemical performances of LSBs. Herein, we report a composite of macro/mesoporous carbon (MMC) coupled with defective TiO2 nanoparticles as a novel functional cathode host for LSBs. The MMC/TiO2 composite has been synthesized using a template-based approach combining simple hydrothermal reactions. Experimental characterizations, electrochemical measurements, and first-principles density functional theory (DFT) calculations disclose that the combination of macro/mesoporous carbon and defective TiO2 (coexistence of oxygen vacancies and Ti3+) effectively suppresses the undesired polysulfide shuttling effect and promotes fast redox conversion of polysulfides during cycling. The resultant LSBs with MMC/TiO2@S as a composite cathode thus exhibit impressive electrochemical properties with high capacity (1420 mAh/g at 0.2C), good rate capability (522 mAh/g at 2C), and cycling ability (65.6% retention at 0.2C over 60 cycles). This work can present some new insights into the rational design and exploration of novel material systems and compositions for applications in LSBs.

Graphene oxide wrapped hollow mesoporous carbon spheres as a dynamically bipolar host for lithium–sulfur batteries

“…08-0247). 55 The sharp diffraction peaks indicate the high crystallinity of the pure sulfur powder with large crystallite sizes, which is not suitable for direct usage in LSBs due to its very low electronic conductivity. The XRD of graphene oxide (GO) flakes shows one strong diffraction peak at about ∼10.4°, possibly from the sub-nanometer-sized ordered areas of moiré patterns formed on rotationally defective bilayer graphene.…”

“…A large, broad band with binding energies (BEs) at 284.6 eV signies the presence of C-C/ C]C bonds of partially graphitized carbon. 55 Another band centered around 285.7 eV suggests the existence of C-O/C-S bonds in the product. The formation of a C-S bond further claries the high affinity of nonpolar carbon towards nonpolar sulfur.…”

Realizing fast polysulfides conversion within yolk-shelled NiO@HCSs nanoreactor as cathode host for high-performance lithium-sulfur batteries

“…36 Furthermore, they also designed a cathode host which combines a macro/mesoporous carbon framework with defective TiO 2 , exhibiting impressive electrochemical properties. 37 However, most traditional metal oxide materials are coupled with conductive polymers or carbon-based frameworks to increase the overall conductivity of the electrode rather than using their intrinsic conductivity to obtain high-performance Li-S batteries, resulting in a lack of controllable morphologies to utilize their structure-efficiency advantages. 38,39 Herein, we synthesize a yolk-shell nanoreactor with a nanoparticle NiO-core and a conductive carbon-shell.…”

Visible-Light-Active Black TiO2 Nanoparticles with Efficient Photocatalytic Performance for Degradation of Pharmaceuticals

“…Because of its tunable bandgap and surface disorder [ 13 ], the presence of point defects such as Ti interstitial, Ti 3+ , surface oxygen vacancies, and the fast electron–hole separation [ 14 ], the black TiO 2 is a more attractive visible light photocatalyst than white TiO 2 . Over the past ten years, it has become attractive for anode applications in electrochemical pollutant degradation from wastewater under sunlight conditions [ 15 ] for solar energy conversion [ 16 ], for cathode applications for lithium–sulfur batteries as the next generation of electrochemical energy storage systems [ 17 , 18 ], and for electron transporter layers in planar perovskite solar cells [ 19 ] and supercapacitors [ 20 ].…”