Reversible Sodiation of Electrochemically Deposited Binder‐ and Conducting Additive‐Free Si–O–C Composite Layers

Abstract

Binder‐ and conducting additive‐free Si–O–C composite layers are deposited electrochemically under potentiostatic conditions from sulfolane‐based organic electrolyte. Quartz crystal microbalance with damping monitoring is used for evaluation of the layer growth and its physical properties. The sodiation–desodiation performance of the material is afterward explored in Na‐ion electrolyte. In terms of specific capacity, rate capability, and long‐term electrochemical stability, the experiments confirm the advantages of applying the electrochemically formed Si–O–C structure as anode for Na‐ion batteries. The material displays high (722 mAh g−1) initial reversible capacity at j = 70 mA g−1 and preserves stable long‐term capacity of 540 mAh g−1 for at least 400 galvanostatic cycles, measured at j = 150 mA g−1. The observed high performance can be attributed to its improved mechanical stability and accelerated Na‐ion transport in the porous anode structure. The origin of the material electroactivity is revealed based on X‐Ray photoelectron spectroscopic analysis of pristine (as deposited), sodiated, and desodiated Si–O–C layers. The evaluation of the spectroscopic data indicates reversible activity of the material due to the complex contribution of carbon and silicon redox centers.