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Characterisations and Electrochemical Performances of Hard Carbons in Sodium Ion Batteries
Carbons have been extensively studied in the literature as Na-Ion anodes: hard carbons, carbon black, carbon nanospheres, carbon fibers and graphene.
Carbon nanotubes made from polyaniline pyrolysis showed interesting performances. A reversible capacity of 250 mAh/g at a current density of 50 mA/g was obtained with 82% of capacity retention after 400 cycles. However the initial coulombic efficiency remains very low (around 50%) [3].
Ding et al. [4] tested carbon made from peat pyrolysis as anode for Na ion batteries. They obtained a reversible capacity of 255mAh/g after 200 cycles with a current density equal to 50 mA/g.
In our study, hard carbons (HC) were made from cellulose. Different final pyrolysis temperatures were studied from 700°C to 1600°C. Characterisation methods such as Small Angle X ray Scattering (SAXS) measurements; isotherms and Transmission Electron Microscopy (TEM) were performed in order to understand the impact of pyrolysis temperature on carbon structure. This parameter plays a major role on external and internal porosities. Different electrochemical tests were performed to study stability and rate capability of the samples. Figure 1 shows the cycling performances of the sample pyrolysed at 1400°C.
In our presentation, we propose to highlight the characterisations performed on these hard carbons. TEM images could clearly show the different graphene sheet arrangements. With the tests performed on Na//HC cells, we will try to correlate hard carbon structure to electrochemical performances. Perspectives on future studies will be also exhibited.
References
[1] S. Komaba, W. Murata, T. Ishikawa, N. Yabuuchi, T. Ozeki, T. Nakayama, A. Ogata, K. Gotoh, and K. Fujiwara. Electrochemical na insertion and solid electrolyte interphase for hard-carbon electrodes and application to na-ion batteries. Advanced Functional Materials, 21(20):3859–3867, 2011.
[2] X. Zhou, X. Zhu, X. Liu, Y. Xu, Y. Liu, Z. Dai and J. Bao. Ultralong cycle life sodium ion battery anodes using a graphene template carbon hybrid. The Journal of Physical Chemistry, 118:22426-22431,2014.
[3] Y. Cao, L. Xiao, M. L. Sushko, W. Wang, B. Schwenzer, J. Xiao, Z. Nie,
L.V. Saraf, Z. Yang, and J. Liu. Sodium Ion Insertion in Hollow Carbon Nanowires for Battery Applications. Nanoletters,12, 3783−3787, 2012.
[4] J. Ding, H. Wang, Z. Li, A. Kohandehghan, K. Cui, Z. Xu, B. Zahiri, X. Tan, E.M. Lotfabad, B.C. Olsen, and D. Mitlin. Carbon nanosheet frameworks derived from peat moss as high performance sodium ion battery anodes. ACS Nano, 7(12):11004–11015, 2013.
Figure 1. Electrochemical test of Na//HC1400 in 1M NaPF6ethylene carbonate/dimethyl carbonate (EC/DMC) performed at C/10 (where C=372mAh/g) with a constant voltage at 50 mV