Carbon-coated Sn-reduced graphene oxide composite synthesized using supercritical methanol and high-pressure free meniscus coating for Na-ion batteries

A highly stable carbon-coated Sn-reduced graphene oxide (Sn-RGO-C) composite was synthesized via a supercritical methanol, high-pressure free meniscus coating, and subsequent carbothermal reduction route. During calcination, the transition of SnO₂ to metallic Sn⁰ occurred via carbothermal reduction. As a result, 0.25 µm–0.75-μm-sized Sn particles, which were uniformly coated with a carbon layer, were incorporated to the RGO sheets at a high Sn loading of 78 wt%. When tested as an anode in sodium-ion batteries (SIBs), the Sn-RGO-C electrode exhibited a high reversible capacity of 403 mAh g^–1 at 50 mA g^–1 after 150 cycles and a high rate capacity of 375 mAh g^–1 at 5 A g^–1. When paired with a NaNi_0.6Co_0.2Mn_0.2O₂ (NaNCM) cathode as a full-cell SIB, the NaNCM || Sn-RGO-C cell delivered high reversible capacities of 78 mAh g_cathode^–1 after the 50th cycle at an average voltage of ~2.7 V.