Ultrafine SnO2 nanoparticles encapsulated in 3D porous carbon as a high-performance anode material for potassium-ion batteries

A novel nanocomposite of ultrafine SnO2 nanoparticles encapsulated in 3D porous carbon is prepared by freeze-drying followed with sintering and dealloying strategy. The SnO2 nanoparticles are obtained by selective etching of Cu from Cu6Sn5 nanoparticles. The ultrafine oxide nanoparticles together with 3D porous carbon network are highly effective in accommodating the huge volume change of SnO2 during potassiation and depotassiation processes. As a result, the obtained sample presents excellent potassium-ion storage performance including high reversible capacity (270.3 mAh g−1 at 100 mA g−1 after 200 cycles and capacity retention close to 80%), ultralong cycle lifespan and excellent rate performance (144.6 mAh g−1 at 2 A g−1).