Hyperpolarized 129 Xe nuclear magnetic resonance study of mesoporous silicon sponge materials
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Dokyoung Kimb) Department of Anatomy and Neurobiology, School of Medicine, and the Center for Converging Humanities, Kyung Hee University, Seoul 130-701, Republic of Korea
Jinmyoung Joo Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea; and Biomedical Engineering Research Center, Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Republic of Korea
Michael J. Sailor Department of Chemistry and Biochemistry, University of California, San Diego, California 92093-0358, USA
Russell Hopson and Li-Qiong Wanga) Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA (Received 23 January 2017; accepted 3 April 2017)
Mesoporous silicon sponge (MSS) is considered as a promising anode material for lithium ion batteries because of its preformed meso/macro porous structures that can accommodate large volume expansion during the lithiation process and its superior electrochemical performance. Temperature dependent hyperpolarized (HP) 129Xe NMR was applied to characterize the structure and porosity of MSS materials with varying pores and particle sizes. Our results reveal irregular pore structures with the presence of micropores inside the larger meso/macropore channels and each MSS material has its own characteristic pore environment with a varying degree of nonuniformity and connectivity of pores. This study demonstrates that HP 129Xe NMR is a potentially useful tool for providing a fingerprint of the structure and connectivity of the pores for each material, complementary to other characterization techniques.
I. INTRODUCTION
High energy density, long cycle life, and low-cost lithium-ion batteries (LiB) are important for the development of electrical vehicles and portable devices.1,2 Many candidate electrode materials with improved LiB electrode performance focus on increased loading capacity, greater cyclability, and capacity retention after many charge–discharge cycles.3–8 Among these materials, readily available and inexpensive silicon is considered as a promising alternative to graphitized carbon as the anode material for modern LIBs because of its higher loading capacity and reduced safety concern.9 However, the large volume expansion (.300%) during the lithiation process leads to the pulverization of silicon particles (.200 nm), the disruption of electron-conducting paths and considerable microstructural reorganization. As a result, crystalline silicon electrodes tend to lose reversible capacity very rapidly.10–13 Contributing Editor: Paolo Colombo a) Address all correspondence to this author. e-mail: [email protected] b) These authors contributed equally. DOI: 10.1557/jmr.2017.151
To overcome the pulverization problem, considerable effort has been devoted to the development of nanostructured Si anode materials. Mesoporous silicon sponge (MSS) with its preformed meso/macro pore structures has been demonstrated in a recent study by in situ transmission electron microscopy (TEM) and continuum media mechanical calcula
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