In Situ Transmission X-ray Microscopy Study on Working SnO Anode Particle of Li-Ion Batteries

The evolution of the interior microstructures of SnO during electrochemical lithiation/de-lithiation has been visualized by in situ transmission X-ray microscopy (TXM), complemented by in situ X-ray diffraction (XRD) to reveal phase information. A SnO secondary particle consisting of plates of primary particles has been shown to homogeneously expand during the first lithiation in two stages, including the first producing Li 2 O matrix that bears most original particle morphology and the second involving full lithiation of the precipitated Sn nano-particles from the first stage. Only the second stage is reversible upon de-lithiation, and the particle undergoes the reversible second-stage deformation during subsequent cycles. The results indicate clear advantages of using such a porous secondary SnO as the anode material in comparison with dense Sn particle previously revealed, including fast lithiation/de-lithiation kinetics, reduced overall volume expansion and enhanced mechanical robustness of the particle, supported by the Li 2 O backbones.