揭示镁热还原过程中 SiO2@C 中无定形碳的部分石墨化现象

IF 5.5 3区材料科学 Q2 CHEMISTRY, PHYSICAL

ACS Applied Energy Materials Pub Date : 2024-07-15 DOI:10.1021/acsaem.4c01115

Min Seok Kang, Sangyeop Kim, Incheol Heo, Won Cheol Yoo

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引用次数: 0

摘要

镁热还原（MR）是一种放热化学反应，可轻易地将 SiO2@C 转化为 Si@C 卵黄结构，这对高能量密度锂离子电池（LIB）具有特别重要的意义。然而，在 MR 过程中，结晶度从无定形碳转变为石墨碳的报道却很少见。在此，我们报告了二氧化硅@碳（SiO2@C）在磁共振过程中部分石墨化以及无定形碳（C）的孔隙堵塞，导致部分石墨化碳（Si@gC）卵壳结构中的硅。MR 过程中产生的放热会影响 C 到 gC 的结晶度，导致孔隙堵塞。在将空心碳（HC）和空心 gC（HgC）用于 LIB 时，由于 HgC 具有更高的导电性和更小的表面积，因此其速率保持率和初始库仑效率（ICE）均优于 HC。因此，当 Si@gC 用于 LIB 时，它显示出出色的 ICE 和速率性能，在 2 C 温度下循环 300 次后仍具有出色的长期稳定性，这清楚地表明了石墨化的有利影响。

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Revealing Partial Graphitization of Amorphous Carbon in SiO2@C during Magnesiothermic Reduction

Magnesiothermic reduction (MR) is an exothermic chemical reaction that can readily convert SiO₂@C to a Si@C yolk structure, which is of particular interest for high-energy-density lithium-ion batteries (LIBs). However, during MR, crystallinity change from amorphous to graphitic carbon has rarely been reported. Herein, we report partial graphitization along with pore blockage of amorphous carbon (C) of SiO₂@C during MR, resulting in Si within the partially graphitized carbon (Si@gC) yolk–shell structure. The exothermic heat generated during the MR affects the crystallinity of C to gC, leading to pore blockage. When hollow C (HC) and hollow gC (HgC) are used for LIBs, HgC exhibits superior rate retention and initial Coulombic efficiency (ICE) than HC owing to higher electrical conductivity and lower surface area. Therefore, when Si@gC is used for LIBs, it shows outstanding ICE and rate performance with excellent long-term stability over 300 cycles at 2 C, clearly demonstrating the beneficial effect of graphitization.

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来源期刊

ACS Applied Energy Materials Materials Science-Materials Chemistry

CiteScore

10.30

自引率

6.20%

发文量

1368

期刊介绍： ACS Applied Energy Materials is an interdisciplinary journal publishing original research covering all aspects of materials, engineering, chemistry, physics and biology relevant to energy conversion and storage. The journal is devoted to reports of new and original experimental and theoretical research of an applied nature that integrate knowledge in the areas of materials, engineering, physics, bioscience, and chemistry into important energy applications.