Biphenyl-Bridged Organosilica as a Precursor for Mesoporous Silicon Oxycarbide and Its Application in Lithium and Sodium Ion Batteries.

Manuel Weinberger,Mika Lindén,Margret Wohlfahrt-Mehrens,Po-Hua Su,Herwig Peterlik

doi:10.3390/nano9050754

Abstract

Silicon oxycarbides (SiOC) are an interesting alternative to state-of-the-art lithium battery anode materials, such as graphite, due to potentially higher capacities and rate capabilities. Recently, it was also shown that this class of materials shows great prospects towards sodium ion batteries. Yet, bulk SiOCs are still severely restricted with regard to their electrochemical performance. In the course of this work, a novel and facile strategy towards the synthesis of mesoporous and carbon-rich SiOC will be presented. To achieve this goal, 4,4′-bis(triethoxysilyl)-1,1′-biphenyl was sol–gel processed in the presence of the triblock copolymer Pluronic P123. After the removal of the surfactant using Soxhlet extraction the organosilica material was subsequently carbonized under an inert gas atmosphere at 1000 °C. The resulting black powder was able to maintain all structural features and the porosity of the initial organosilica precursor making it an interesting candidate as an anode material for both sodium and lithium ion batteries. To get a detailed insight into the electrochemical properties of the novel material in the respective battery systems, electrodes from the nanostructured SiOC were studied in half-cells with galvanostatic charge/discharge measurements. It will be shown that nanostructuring of SiOC is a viable strategy in order to outperform commercially applied competitors.

Highlights

There is an urgent need to reduce greenhouse gas emissions significantly to lower the aftermath of the anthropogenic climate change
This compound is significantly more hydrophobic than water and might form an emulsion together with the biphenyl-bridged silane, which is probably further stabilized by the surfactant P123
Mesoporous carbon-rich silicon oxycarbide has been successfully synthesized by the pyrolysis of a mesoporous organosilica precusor which was synthesized from sol–gel processing of 4,4 -bis(triethoxysilyl)-1,1 -biphenyl in the presence of the triblock copolymer Pluronic P123

Summary

Introduction

There is an urgent need to reduce greenhouse gas emissions significantly to lower the aftermath of the anthropogenic climate change. With the transition to a renewable and sustainable energy infrastructure, batteries will become more and more important, for instance, in order to store energy spillover or to power electric vehicles. Lithium ion batteries based on intercalation chemistry currently represent the state-of-the-art, this technology is limited to energy densities of around 250 Whkg−1 on a full cell level. Electrode materials utilizing alloying or a conversion-based reaction throughout battery operation may exceed energy densities of conventional battery active materials, still, much effort has to be invested to deal with other problems, such as huge volume expansion or poor coulombic efficiencies. Lithium is a rather limited resource, which might at some point lead to a shortage, and increased cost. Other so-called post lithium battery technologies, such as sodium ion batteries, are gaining increasing attention

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Conclusion