Among various rechargeable battery systems, rechargeable Li-sulfur (S) batteries have been proposed as an alternative system for Li-ion secondary batteries because of their high theoretical energy density … Despite its advantageous features, however, the rechargeable Li-S battery is plagued by two major problems. One is the insulating characteristic of S and the other is the solubility of the Li-polysulfides generated during the discharge/charge process in various electrolytes; these problems contribute to significant loss of S during cycling and results in a poor cyclability. … Although … efforts have led to enhanced electrochemical performance of S electrodes, it is still not sufficient for practical utilization.

Se and Te, elements of the same group 16 in the periodic table with S, can alloy with Li to form Li₂Se and Li₂Te, respectively, which demonstrates that Se and Te may be appropriate elements to use as electrodes in rechargeable Li batteries.

—Seo et al.

Used as a cathode material, Se (Selenium) has shown a high capacity close to its theoretical capacity (Li₂Se: 679 mAh g⁻¹). However, it shows low rate capability and poor cycling behavior because of its low electrical conductivity and large volume expansion during cycling.

Although Tellurium has a lower theoretical gravimetric capacity (Li₂Te: 420 mAh g⁻¹) as compared with S and Se, its high density (6.24 g cm⁻³, around three times higher than that of S) provides a high theoretical volumetric capacity (2621 mAh cm⁻³). In addition, the electronic conductivity of Te (2 × 10⁻⁴ MS m⁻¹) is considerably higher than those of S (5 × 10⁻²² MS m⁻¹) and Se (1 × 10⁻¹⁰ MS m⁻¹).

… despite its advantageous features as a prospective electrode material, there are little attempts to apply Te as an electrode for Li secondary batteries. While we are preparing this manuscript, Liu et al. have recently shown a Li-Te battery using an interesting Te/porous carbon composite by a vacuum-liquid-infusion method. Although the result showed a reversible capacity of 224 mAh g⁻¹ at a current rate of 50 mA g⁻¹, it showed a huge irreversible initial capacity corresponding to ca. 780 mAh g⁻¹ originated from a porous carbon. Therefore, a pioneering and fundamental work for realization of Li-Te battery system is needed.

—Seo et al.

In their study, the team from Kumoh prepared and tested various Te/C composites for their suitability as cathode materials for the Li-Te secondary battery system.

Electrochemical behavior of MR-Te/C nanocomposite electrode. (a) Voltage profiles of Te (current density: 10 mA g−1) and MR-Te/C nanocomposite electrodes (current density: 10 and 100 mA g−1). (b) Cycling performance of Te, Te/C nanocomposite, and MR-Te/C nanocomposite electrodes at a cycling rate of 10 or 100 mA g−1. (c) Voltage profiles at various C rates for Li4Ti5O12 and MR-Te/C nanocomposite electrodes. (d) Plot of the discharge and charge capacity vs. cycle number for the Li4Ti5O12 and MR-Te/C nanocomposite electrodes at various C rates (Li4Ti5O12 - 1C: 190 mAh cm−3, MR-Te/C nanocomposite - 1C: 700 mAh cm−3). Seo et al. Click to enlarge.

Resources

• Jeong-Uk Seo, Gun-Kyu Seong & Cheol-Min Park (2015) “Te/C nanocomposites for Li-Te Secondary Batteries” Scientific Reports 5, Article number: 7969 doi: 10.1038/srep07969