Ultrastable Cycle Stability of SnO₂ Quantum Dot Embedded Polypyrrole Anode for Li-Ion Battery

SnO2 is an excellent candidate for replacement of conventional graphite-based anodes in lithium-ion batteries. It offers four times the specific capacity of carbon and a low working potential of ∼0.6 V vs Li+/Li but suffers from large capacity fade due to a drastic volume change (∼300%) upon cycling. A unique design of SnO2 quantum dots (QDs) dispersed over flexible and conducting polypyrrole (PPy) is vital for achieving a high rate capability and long cycle life. This specially designed SnO2 QDs@PPy anode delivers excellent cycle performance with discharge capacities of 1252, 723, 474, 298, and 152 mAh g–1 at discharge rates of 0.35, 0.7, 1, 1.8, and 3.5 A g–1. Upon long cycling at an elevated current density of 2 A g–1, the anode demonstrated an initial discharge capacity of 572 mAh g–1, while retaining 399 mAh g–1 at the 1360th cycle with a very low capacity decay of 0.022% per cycle. The superior mechanical stability and conductivity of the specially designed composite may be the reason behind very high cycle stability.