2Material Science and Technology of Japan, 55（2018）160～167

Oct. 2018

Regular Paper
Synergistic Effect of Polar TiO2 and Conductive Carbon in Freestanding
TiO2/C Electrode for Li-Polysulfide Battery
Anteneh Marelign BEYENE, Jong Hyuk YUN, Syed Abdul AHAD, Brindha MOORTHYand Do Kyung KIM*
Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology(KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea
Received Aug. 22, 2018; accepted for publication Sep. 20, 2018
Abstract
Li-S battery system is one of the promising candidates for the next generation energy storage demands as it has
strong potential to provide two to three times higher energy density than the state of the art Li-ion battery. However,
the highly insulative nature of sulfur and the high solubility and diffusivity of intermediate polysulfides (PSs) have
impeded the realization of this potentially promising battery system by significantly reducing its performance. Efforts
have been made to address these problems by compositing sulfur with different carbon nanostructures, which at thesame time confine the PSs physically and reduce their diffusivity. The physical entrapment of PSs using different
carbon nanostructures has brought some degree of performance improvement; nevertheless, for long term cycling
chemical entrapment using polar materials was found to be more effective. TiO2 is among the various polar hosts thathave brought remarkable performance improvement in Li-S battery systems. Despite the strong polar nature of TiO2,
it is poor electronic conductive demands to be mixed with conductive carbon to be used as a sulfur host. In this work
we attempted for the first time to use a 1-D TiO2/carbon mixture for a freestanding electrode design to achieve a
relatively high sulfur loading of 2.5 mg/cm2. The influence of different TiO2/C compositions on the electrochemical
performance of the cells also has been discussed.
Keywords: Lithium-polysulfide batteries, Polar host, Titanium dioxide, Conductive carbon, Freestanding electrode1.

Introduction

problems since sulfur was first used as cathode in a Li-S battery

The Li-sulfur battery is one of the promising candidates forsystem. The majority of Li-S based research has focused on thenext-generation energy storage demand [1-4]. On the basis of thecathode part, although some groups have studied the anode,high abundance of sulfur, its relative low mass, and its ability toseparator, and the electrolyte as well.
Earlier

adopt a wide variety of oxidation states the Li-S battery hasreports

focus

on

using

different

carbonremarkable potential for low cost and high energy density

nanostructures for making a carbon-sulfur composite cathode inbatteries [5,6]. Nevertheless, there are challenges that impede

order to create a conductive network in the composite cathodethe realization of the full potential of Li-Sulfur batteries. Theand physically entrap polysulfides. It was possible to achieve

fundamental challenges in the Li-Sulfur system are the highly

remarkable performance improvement by employing different

insulating nature of sulfur and lithium sulfides, the dissolution ofcarbon nanostructures with different cathode architecture [10].

polysulfides in the electrolyte and a consequent shuttling

However, the physical entrapment was not strong enough to holdproblem, high volume expansion at the cathode, and dendrite

the polysulfides during long term cycling. Eventually theformation at the anode [5,7–9]. The aforementioned problems arepolysulfides dissolve into the electrolyte and migrate to theexacerbated when high sulfur loading is employed at the cathode.

anode, leading to active material loss, accumulation of an

Numerous studies have been carried out to alleviate theseinsulating layer at the anode, and consequent capacity fading.
Chemical entrapment of polysulfides using multifunctional*Corresponding author: (dkkim@kaist.ac.kr)(160)