Reduced expansion and improved full-cell cycling of a SnOx#C embedded structure for lithium-ion batteries

Abstract

SnO_x exhibits a much larger theoretical capacity compared to graphite as an anode material in lithium-ion batteries (LIBs). However, the cycling stability and initial coulombic efficiency (ICE) of SnO_x based electrodes need to be improved. In this study, by coating carbon on a dried SnO_x electrode film using one-step chemical vapor deposition, a SnO_x#C composite is obtained, wherein ∼70 nm sized SnO_x nanoparticles are uniformly dispersed and embedded in a carbon matrix. Owing to its relatively small electrochemical surface area and mechanical robustness, the ICE is largely improved from ∼40% to >65%. Besides, a Li-matched full cell with 36% excess LiCoO₂ cathode material can run stably for more than 100 cycles at 0.1 A g⁻¹, delivering a gravimetric and a volumetric capacity of 456 mA h g⁻¹ and 644 mA h cm⁻³, respectively, which are superior to graphite. The lithiation/delithiation process of SnO_x#C observed using an in situ transmission electron microscope technique reveals that the embedded structure expands by only ∼5%. Besides, the thickness increment of the electrode film after 100 cycles is measured to be 32%, which is much smaller than the acceptable 50% in the LIB industry, illustrating the good stability of the solid-electrolyte interphase (SEI) skeleton.