A Novel Carbon Supported Tellurium Electrode for Lithium and Sodium Secondary Batteries
Authors: Koketsu Toshinari , Strasser Peter , Wu Chao , Huang Yunhui 
Published: February 2020

Recently, Se was reported as a promising novel positive electrode active material from several research groups (1-3). Se has better conductivity (˜10-3 S cm-1) than S and several studies on Li-Se/carbon composite cell showed important characteristics such as a very limited redox shuttle effect, and much higher activity. It is noteworthy that Se/carbon composites are also used as Na+-ion intercalation/de-intercalation electrode at room temperature. As the Se shows quite different electrochemical properties from S, Te can be also a candidate for a cathode active material (4, 5).

We recently reported that Li-Te@CMK-3 battery showed very high C-rate capability with excellent durability (6). The electrochemical reactions during charge-discharge tests are complete oxidation and reduction of Te by following reaction: Te + 2Li+ + 2e- ↔ Li2Te. The theoretical capacity is 420 mA h g-1 and redox potential is 1.80 V vs. Li+/Li. Compared with Se, higher electroconductivity of Te (5 S cm-1) and higer density (6.24 g cm-2) would be advantageous for high rate charge-discharge test.

In this contribution, we show that our novel Te@CMK-3 composite electrode also works for Na intercalation/de-intercalation. The expected chemical reaction is the complete oxidation and reduction of Te by following reaction: Te + 2Na+ + 2e- ↔ Na2Te  (theoretical potential is 1.57 V vs. Na+/Na). Considering this relatively lower working potential, this electrode can be possibly used for negative electrode of Na secondary battery. CMK-3 was synthesized using SBA-15 as substrate based on the previous report (7). Te@CMK-3 composite was synthesized by melt diffusing strategy. The confinement of Te was confirmed by SEM, XRD, and BET measurements. A Na-Te@CMK-3 cell showed plateau between 1.0-1.5 V vs. Na+/Na during the discharge test. The Na-Te@CMK-3 cell also showed very high C-rate capability with good durability. Almost no capacity degradation was observed after 500 cycles of charge-discharge test at 1C-rate. The coulombic efficiency of every single cycle was close to 100 %, which means sodiation/desodiation of Te is quite reversible. The specific discharge capacity at every C-rate was approximately 76 % (0.2C), 68 % (0.5C), 61 % (1C), and 52 % (2C) of theoretical specific capacity. Here, the C-rate of 0.5C, 1C, 2C are corresponding to 210 mA g-1, 420 mA g-1, 840 mA g-1, and 1680 mA g-1, respectively. We firstly demonstrated that Te@CMK-3 composite electrode worked as a Na-ion intercalation/de-intercalation electrode and preliminary studies showed superior rate capability and cyclability. This work is crucial for developing high power density output Na secondary batteries.

References

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2.  A. Abouimrane, D. Dambournet, K. W. Chapman, P. J. Chupas, W. Weng and K. Amine, Journal of the American Chemical Society, 134, 4505 (2012).

3.  C. P. Yang, S. Xin, Y. X. Yin, H. Ye, J. Zhang and Y. G. Guo, Angewandte Chemie, 52, 8363 (2013).

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5.  J. Zhang, Y. X. Yin, Y. You, Y. Yan and Y. G. Guo, Energy Technol-Ger, 2, 757 (2014).

6.  T. Koketsu, P. Strasser, C. Wu and Y. Huang,  LiBD2015 Electrode Materials Meeting abstracts, Arcachon, France (2015).

7.  X. Ji, K. T. Lee and L. F. Nazar, Nature materials, 8, 500 (2009).

Figure 1