New Insights in to the Lithium Storage Mechanism in Polymer Derived SiOC Anode Materials
New Insights in to the Lithium Storage Mechanism in Polymer Derived SiOC Anode Materials
复制标题
DOI：
10.1016/j.electacta.2013.12.037
复制
发表时间：
2014-02
影响因子：
6.6
通讯作者：
V. Pradeep;M. Graczyk‐Zajac;R. Riedel;G. Sorarù
中科院分区：
文献类型：
--
作者：
V. Pradeep;M. Graczyk‐Zajac;R. Riedel;G. Sorarù
以1,3,5,7-四甲基1,3,5,7-四乙烯基环四硅氧烷或二乙烯基苯为交联剂，对聚羟基甲基硅氧烷制备的预陶瓷聚合物进行热解制备聚合物衍生的氧化硅（SiOC）材料。热解在1000℃和1300℃的惰性气氛中进行。通过改变起始前驱体的量来改变SiOC的碳含量，保持O/Si原子比不变，约为1。电化学测量是为了评估材料作为锂离子电池阳极的应用。详细的结构表征研究是使用互补技术进行的，目的是将电化学行为与SiOC阳极的结构联系起来。结果表明，SiOC阳极表现为一种由无序的碳化硅氧相和自由的C相组成的复合材料，其第一插入容量高达1300 mAh g−1。然而，不可逆的电荷被困在非晶氧碳化硅网络中也很高，因此在高碳含量的SiOCs上测得的最大可逆锂存储容量为650mAh g−1，在这种情况下，非晶氧碳化硅和自由C相之间的平衡是最佳的。高碳SiOC在高充放电速率下也表现出优异的循环稳定性和性能：在2c速率下的可逆容量约为200 mAh g−1。提高热解温度对低碳和高碳材料的影响相反，低碳材料的可逆容量呈已知趋势下降，而高碳材料的可逆容量呈增加趋势，这是同类材料从未见过的。
Polymer derived silicon oxycarbide (SiOC) materials are prepared by the pyrolysis of preceramic polymers obtained from polyhydridomethylsiloxane using 1,3,5,7-tetramethyl1,3,5,7-tetravinyl cyclotetrasiloxane or divinyl benzene as a cross-linking agent. The pyrolysis is carried out in an inert atmosphere at 1000 and 1300 °C. The carbon content of SiOC is varied by changing the amount of starting precursors maintaining the same O/Si atomic ratio of about 1. Electrochemical measurements are performed in order to evaluate the materials in terms of their application as anodes in Li-ion batteries. Detailed structural characterization study is performed using complementary techniques with the aim of correlating the electrochemical behavior with the structure of the SiOC anodes. Results suggest that SiOC anodes behave as a composite material consisting of a disordered silicon oxycarbide phase having a very high first insertion capacity of ca 1300 mAh g−1and a free C phase. However, the charge irreversible trapped into the amorphous silicon oxycarbide network is also high and therefore the maximum reversible lithium storage capacity of 650mAh g−1is measured on high-C content SiOCs for which the balance between the two phases, namely the amorphous silicon oxycarbide and the free C phase, is optimal. The high carbon content SiOC show also an excellent cycling stability and performance at high charging/discharging rate: the reversible capacity at 2 C rate being around 200 mAh g−1. Increasing the pyrolysis temperature has an opposite effect on the low-C and high-C materials: for the latter one the reversible capacity decreases following a known trend while the former shows an increase of the reversible capacity which has never been observed before for similar materials.