Lithiation-Induced Structural Rearrangement and Stress Change in SiCO-Derived Porous Carbon: A First-Principles Study

Abstract

Silicon oxycarbide (SiCO)-derived porous carbon is a promising anode material for high-power lithium-ion batteries with large reversible capacity and high rate performance. In this work, porous carbon compounds with various morphologies are successfully reproduced by simulating the etching process of SiCO and then lithiation-induced structural rearrangement and stress change in porous carbon are investigated using first-principles calculations. Upon insertion of lithium, Si−C/O mixed-bond units are destroyed with breaking of Si−O bonds, the lithium atoms prefer to form bonds with oxygen, and the pores are gradually filled with the Li−O complex. The negative stress of the lithiated system indicates local compression of Si−C/O units, which is also demonstrated by the shorter Si−O bonds and enhanced bulk modulus. The local compression is related to constraint of the carbon network that act as a buffering structure to limit volume expansion during lithiation, and the increase and decrease in normal stress are related to the stretching and breaking of the carbon network. Moreover, it is revealed that the lithium content that corresponds to the maximum stress can be used to estimate the specific capacity of the system. Our analysis of the lithiation process provides a conceptual foundation for future design of porous carbon-based anode materials.

A review of silicon oxycarbide ceramics as next generation anode materials for lithium-ion batteries and other electrochemical applications

“…72 However, it has been reported that local compressive stresses are generated in the lithiated systems resulting in the shortening of bond lengths and a higher bulk modulus. 77 This also means that the local stress generated can be used to measure the system's specific capacity. Moreover, it is observed that replacing oxygen with nitrogen in these systems makes it unattractive for lithium intercalation due to the highly covalent nature of Si–N bonds and the lower electron density of nitrogen atoms.…”