Titan 80 300 environmental tem

The in situ TEM measurements were performed in Titan 80-300 environmental TEM (FEI) at the acceleration voltage of 300 kV using a dual-probe electrical biasing holder (Nanofactory Instruments). The QMS (or Si) particles were drop-cast onto a gold wire as a working electrode, while a piece of lithium was attached to a tungsten rod served as the counter electrode. During the transfer of the holder into the TEM, the Li metal was shortly exposed to air for about 3 s to create a thin Li₂O layer acting as a solid electrolyte. A constant potential of ±3 V was applied to the QMS (or Si) electrodes against the Li metal during lithiation and delithiation, whereby Li-ion was inserted and extracted through the solid electrolyte. It does not make sense for us to estimate the ion conductivity of particle itself during in situ TEM analysis, because it was measured using the lithium oxide solid electrolyte and each measurement had a different voltage bias depending on its size and contact features. Nevertheless, the QMS particles can be lithiated faster than that of Si even with a lower bias of −3 V as compared with our previous report^{7 (link)}.

FIB/SEM imaging and TEM specimen preparation by FIB lift out were conducted on a FEI Helios DualBeam FIB operating at 1–30 kV. STEM observation was conducted on FEI Titan 80-300 TEM with probe corrector. In STEM mode the beam current is 60 pA. For high-resolution lattice imaging, the beam dose is around 10⁶ e Å^–2. HRTEM observations were conducted on FEI Titan 80-300 Environmental TEM with objective lens corrector. The beam current is 140 pA. The in situ TEM heating holder is carried using a double tilt holder based on resistant heating coil made by Gatan (Gatan Inc., Pleasanton, CA, USA). The sample was heated at a constant rate of 5 °C min^–1 from room temperature and the temperature is measured using a thermal couple integrated into the holder. In situ XRD experiments were carried out using a Bruker D8 advace X-ray diffractometer with a heating stage.