New Insights into Understanding Irreversible and Reversible Lithium Storage within SiOC and SiCN Ceramics.

Magdalena Graczyk-Zajac,Gian-Domenico Soraru,Jan Kaspar,Pradeep Sasikumar,Lukas Reinold,Ralf Riedel

doi:10.3390/nano5010233

Magdalena Graczyk-Zajac, Gian-Domenico Soraru + Show 4 more

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https://doi.org/10.3390/nano5010233

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Abstract

Within this work we define structural properties of the silicon carbonitride (SiCN) and silicon oxycarbide (SiOC) ceramics which determine the reversible and irreversible lithium storage capacities, long cycling stability and define the major differences in the lithium storage in SiCN and SiOC. For both ceramics, we correlate the first cycle lithiation or delithiation capacity and cycling stability with the amount of SiCN/SiOC matrix or free carbon phase, respectively. The first cycle lithiation and delithiation capacities of SiOC materials do not depend on the amount of free carbon, while for SiCN the capacity increases with the amount of carbon to reach a threshold value at ~50% of carbon phase. Replacing oxygen with nitrogen renders the mixed bond Si-tetrahedra unable to sequester lithium. Lithium is more attracted by oxygen in the SiOC network due to the more ionic character of Si-O bonds. This brings about very high initial lithiation capacities, even at low carbon content. If oxygen is replaced by nitrogen, the ceramic network becomes less attractive for lithium ions due to the more covalent character of Si-N bonds and lower electron density on the nitrogen atom. This explains the significant difference in electrochemical behavior which is observed for carbon-poor SiCN and SiOC materials.

Highlights

Due to increasing energy consumption and environmental aspects, there is a growing interest for new energy related materials
As the high carbon content of the aforementioned ceramic systems seems to play an important role in the reversible storage of Li-ions, our work focused on the development of carbon-rich Si-based polymer derived silicon carbonitride (SiCN) and silicon oxycarbide (SiOC) anode materials for lithium-ion batteries
We evaluate what kind of microstructural properties of the Si(O,N)C ceramic determine the reversible and irreversible capacities and long cycling stability and we identify the major differences in the lithium storage sites within SiCN and Figures 1a and 2a present the dependence of the first cycle delithiation capacity and cycling stability (The cycling stability has been calculated as the ratio of the delithiation capacity after prolonged cycling (>100 cycles) to the first extraction capacity), both registered with low currents (C/10–C/20)

Summary

Introduction

Due to increasing energy consumption and environmental aspects, there is a growing interest for new energy related materials. Though Dahn et al filed a patent related to the use of silazane-derived SiCN ceramics in 1997 which show reversible discharge capacities up to 560 mAh·g−1 [44], much less research has been done since that time on the application of these materials in lithium-ion batteries in comparison to SiOC.

Results

Conclusion