USC Viterbi team integrating silicon anode and sulfur-based cathode for Lithium-sulfur battery with low fabrication cost
1 April 2014
USC Viterbi School of Engineering professor Chongwu Zhou and his research team have developed a silicon nanoparticle anode and a sulfur-based cathode with low fabrication cost and high electrode performance for rechargeable lithium-sulfur batteries.
The effort builds on their earlier work in developing nanostructured silicon materials for use as high performance lithium-ion battery anodes (earlier post), with a focus on developing a cost-effective method for producing Si nanoparticles, which they accomplish via ball-milling of metallurgical Si and inexpensive stain-etching. In a paper in the ACS journal Nano Letters, they report nanoporous Si anodes with a reversible capacity of 2,900 mAh/g attained at a charging rate of 400 mA/g (0.1 C), with 10 cycles measured and a capacity above 1100 mAh/g at 2000 mA/g (0.5 C) with extended 600 cycles measured.
The approach in this study compares more favorable than many other approaches in the production cost. For example, while the reported capacity of porous Si prepared through a disproportion reaction of SiO is comparable to our results, SiO is of higher price than the metallurgical Si studied in this work, and the disproportion of SiO at high temperature requires a large thermal budget.
We believe further optimization of porous structures will lead to an even higher capacity and longer cyclic life. The study of the compatibility of Si anode with cathode materials such as LiMn2O4, LiFePO4, and sulfur also deserves further endeavors to harvest the full potential of the porous Si anodes.—Ge et al.
In addition, graduate student Jiepeng Rong and other team members developed a method of coating sulfur powder with graphene oxide (GO) to improve performance in lithium-sulfur batteries. This work is reported in a separate paper in Nano Letters.
… the wrapping of graphene oxide on sulfur has stimulated a lot of interest due to the potential use as lithium−sulfur (Li−S) battery cathodes. Li−S batteries are promising candidates to power up electric vehicles because of their high theoretical energy density of 2567 Wh kg−1, which is more than 5 times that of lithium-ion batteries based on traditional insertion compound cathodes. Other advantages of Li−S batteries are that elemental sulfur is low cost, low toxic, and abundant.
However, the practical application of Li−S batteries is greatly hindered by three major challenges including (1) dissolution of intermediate polysulphide into electrolyte, (2) poor electronic conductivity of sulfur, and (3) large volumetric expansion of sulfur upon lithiation, which result in rapid capacity decay and low Coulombic efficiency. Encapsulating sulfur particles with conducting materials, such as graphene oxide, can improve their electronic conductivity and limit polysulphide dissolution simultaneously.
… We note that complete wrapping of graphene oxide on sulfur particles may be the key to mitigate polysulphide dissolution and may reveal itself in improved cycling stability. In this letter, we report a facile and robust method that is capable of coating GO uniformly on various particles with arbitrary sizes, geometries, and compositions, by engineering the ionic strength in various aqueous solutions.—Rong et al.
In their study, the team produced sulfur/GO core−shell particles as Li−S battery cathode material showing superior specific capacity of 800 mAh/g after 1000 cycles at 1 A/g current rate if only the mass of sulfur is taken into calculation, and 400 mAh/g if the total mass of sulfur/GO is considered. Most importantly, the capacity decay over 1000 cycles is less than 0.02% per cycle.
The team is now working to test the silicon anode and sulfur cathode together in a complete battery.
As far as we can tell, our technologies with both the silicon anode and sulfur cathode are among the most cost-effective solutions and therefore show promise for commercialization to make the next-generation of lithium-ion batteries to power portable electronics and electric vehicles.—Jiepeng Rong
M.Y. Ge, Y.H Lu, P. Ercius, J.P. Rong, X Fang, C.W. Zhou, M. Mecklenburg (2014) “Large-Scale Fabrication, 3D Tomography, and Lithium-Ion Battery Application of Porous Silicon,” Nano Letters, 14, 261 doi: 10.1021/nl403923s
J.P. Rong, M.Y. Ge, X. Fang, C.W. Zhou (2014) “Solution Ionic Strength Engineering As a Generic Strategy to Coat Graphene Oxide (GO) on Various Functional Particles and Its Application in High-Performance LithiumSulfur (LiS) Batteries,” Nano Letters, 14, 473 doi: 10.1021/nl403404v
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