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

SnOx 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 SnOx based electrodes need to be improved. In this study, by coating carbon on a dried SnOx electrode film using one-step chemical vapor deposition, a SnOx#C composite is obtained, wherein ∼70 nm sized SnOx 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 SnOx#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.