Fully reversible lithium storage of tin oxide enabled by self-doping and partial amorphization

SnO₂ has a high theoretical capacity of 1493 mA h g^-1 as an anode material for Li-ion batteries, but its full reversibility is difficult to achieve upon cycling due to the sluggish kinetics. We for the first time demonstrate a fully reversible SnO₂ anode for Li-ion batteries enabled by self-doping and partial amorphization by anchoring its nanoparticles on a graphene/single walled carbon nanotube hybrid framework. The uniquely structured nanocomposite containing 74% SnO₂ exhibits high reversible capacities together with good rate and cycling capabilities. For instance, the composite anode retains an overall capacity of 1215 mA h g^-1 (1425 mA h g^-1 for SnO₂) after 200 cycles at 0.1 A g^-1, which is very close to its theoretical capacity. Moreover, an overall capacity of 947 mA h g^-1 (1062 mA h g^-1 for SnO₂) can be delivered at a higher rate (1 A g^-1) with 98% capacity retention over 350 cycles. This exceptional performance can be attributed to the formation of highly dispersed metallic Sn in the Li₂O matrix during cycling, which is caused by the unique two-step lithiation mechanism of the self-doped and partially amorphous SnO₂ nanoparticles. A similar strategy can also be applied to develop other high-performance electrodes with conversion reactions.