Rational Engineering of p‐n Heterogeneous ZnS/SnO2 Quantum Dots with Fast Ion Kinetics for Superior Li/Na‐Ion Battery

Abstract Constructing heterogeneous nanostructures is an efficient strategy to improve the electrical and ionic conductivity of metal chalcogenide‐based anodes. Herein, ZnS/SnO 2 quantum dots (QDs) as p‐n heterojunctions that are uniformly anchored to reduced graphene oxides (ZnS‐SnO 2 @rGO) are designed and engineered. Combining the merits of fast electron transport via the internal electric field and a greatly shortened Li/Na ion diffusion pathway in the ZnS/SnO 2 QDs (3–5 nm), along with the excellent electrical conductivity and good structural stability provided by the rGO matrix, the ZnS‐SnO 2 @rGO anode exhibits enhanced electronic and ionic conductivity, which can be proved by both experiments and theoretical calculations. Consequently, the ZnS‐SnO 2 @rGO anode shows a significantly improved rate performance that simple counterpart composite anodes cannot achieve. Specifically, high reversible specific capacities are achieved for both lithium‐ion battery (551 mA h g −1 at 5.0 A g −1 , 670 mA h g −1 at 3.0 A g −1 after 1400 cycles) and sodium‐ion battery (334 mA h g −1 at 5.0 A g −1 , 313 mA h g −1 at 1.0 A g −1 after 400 cycles). Thus, this strategy to build semiconductor metal sulfides/metal oxide heterostructures at the atomic scale may inspire the rational design of metal compounds for high‐performance battery applications.