A Robust and Conductive Black Tin Oxide Nanostructure Makes Efficient Lithium‐Ion Batteries Possible

SnO2‐based lithium‐ion batteries have low cost and high energy density, but their capacity fades rapidly during lithiation/delithiation due to phase aggregation and cracking. These problems can be mitigated by using highly conducting black SnO2−x, which homogenizes the redox reactions and stabilizes fine, fracture‐resistant Sn precipitates in the Li2O matrix. Such fine Sn precipitates and their ample contact with Li2O proliferate the reversible Sn → Li xSn → Sn → SnO2/SnO2−x cycle during charging/discharging. SnO2−x electrode has a reversible capacity of 1340 mAh g−1 and retains 590 mAh g−1 after 100 cycles. The addition of highly conductive, well‐dispersed reduced graphene oxide further stabilizes and improves its performance, allowing 950 mAh g−1 remaining after 100 cycles at 0.2 A g−1 with 700 mAh g−1 at 2.0 A g−1. Conductivity‐directed microstructure development may offer a new approach to form advanced electrodes.