Polymer衍生的SiOC与石墨烯气凝胶集成作为高稳定性锂离子电池阳极
Polymer-Derived SiOC Integrated with a Graphene Aerogel As a Highly Stable Li-Ion Battery Anode
摘要：
无定形聚合物衍生的碳氧化硅（SiOC）作为石墨的替代物是锂离子电池阳极的有吸引力的候选物，石墨的理论容量限于372 mAh/g。然而，SiOC往往表现出差的传输性能和循环性能，作为稀疏分布的碳簇和低效的活性位点的结果。为了克服这些限制，我们通过将聚合物前体溶剂辅助渗透到改性的三维石墨烯气凝胶骨架中来设计和制造层状石墨烯SiOC异质结构。高熔点溶剂的使用促进了前体的冷冻干燥，其在热解之后产生SiOC作为负载在氮掺杂的还原氧化石墨烯气凝胶的表面上的层。这里采用的制造方法修改的SiOC相的组成和微观结构。在所研究的材料中，对于中等SiOC含量的样品获得了最高水平的性能，其中石墨烯网络占系统的19.8重量%。在这些材料中，在低充电速率下实现了751 mAh/g的稳定可逆充电容量。在1480 mA/g的高充电速率下，容量保持率约为1.5%。95%（352 mAh/g）。在所有速率下，第一次循环后库仑效率保持在99%以上。与无支撑的SiOC相比，石墨烯气凝胶SiOC纳米复合材料的所有指标的性能都有很大提高。该性能归因于跨多个长度尺度的机制。富氧的SiO 4-xCx四面体单元和SiOC内的连续游离碳网络的存在提供了用于可逆锂化的位点，而层状石墨烯SiOC异质结构提供了高离子和电子传输。
英文摘要：
Amorphous polymer derived silicon oxycarbide (SiOC) is an attractive candidate for Lithium ion battery anodes, as an alternative to graphite, which is limited to a theoretical capacity of 372 mAh/g. However, SiOC tends to exhibit poor transport properties and cycling performance as a result of sparsely distributed carbon clusters and inefficient active sites. To overcome these limitations, we designed and fabricated a layered graphene SiOC heterostructure by solvent assisted infiltration of a polymeric precursor into a modified three dimensional graphene aerogel skeleton. The use of a high melting point solvent facilitated the precursors freeze drying, which following pyrolysis yielded SiOC as a layer supported on the surface of nitrogen doped reduced graphene oxide aerogels. The fabrication method employed here modifies the composition and microstructure of the SiOC phase. Among the studied materials, the highest levels of performance were obtained for a sample of moderate SiOC content, in which the graphene network constituted 19.8 wt % of the system. In these materials, a stable reversible charge capacity of 751 mAh/g was achieved at low charge rates. At high charge rates of 1480 mA/g, the capacity retention was ca. 95% (352 mAh/g) after 1000 consecutive cycles. At all rates, Coulombic efficiencies greater than 99% were maintained following the first cycle. Performance across all indicators was majorly improved in the graphene aerogel SiOC nanocomposites, compared with unsupported SiOC. The performance was attributed to mechanisms across multiple length scales. The presence of oxygen rich SiO4-xCx tetrahedral units and a continuous free carbon network within the SiOC provides sites for reversible lithiation, while high ionic and electronic transport is provided by the layered graphene SiOC heterostructure.
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