Fabrication of Internal Electric Field Sns/Sb₂S₃ with Engineered Porous Structure for Fast Kinetics Sodium Ion Storage

Benefiting from the abundance and low cost of sodium, sodium-ion batteries show great potential as lithium-ion batteries in application of large-scale energy storage. However, anode material graphite with high theoretical capacity 372 mAh g -1 , low charge-discharge plateau potential and good cyclability, widely applied in lithium-ion batteries, exhibited poor electrochemical performance. The larger radius of Na-ion compared to Li-ion hinders the mass and ion transfer during charge-discharge cycling. Thus, anode material with large abundance, stability and high conductivity is crucial for the development and further application of sodium-ion batteries. Sodium-ion batteries have the potential to benefit greatly from metallic sulfide anodes, which offer high theoretical capacities. Unfortunately, the practical use of these anodes is limited by poor electrochemical performance, as sulfides tend to expand significantly in volume and Na + ions exhibit sluggish kinetics during cycling. We have developed a facile and scalable approach to synthesizing a SnS/Sb 2 S 3 heterostructure that is porous and bimetallic, with an additional sulfur and nitrogen co-doped carbon matrix encapsulation (SnS/Sb 2 S 3 @SNC). The PAN precursor is mixed homogeneously with SnSbx and S with a ball milling process. The sulfur evaporates from the mixture and reacts with the SnSb x alloy, leading to the formation of bimetallic sulfides SnS/Sb 2 S 3 . As a result, voids are generated, which in turn contributes to the development of a porous structure. At the same time, the PAN is carbonized, generating a S, N co-doped carbon matrix. SnS and Sb 2 S 3 are two highly promising anode materials for sodium-ion batteries, with high theoretical specific capacity of 1022 mAh g -1 and 947 mAh g -1 , respectively. Moreover, bimetallic sulfides possess different bandgap make them ideal components for generating a strong internal electric field on the hetero-interface, which allows to improve the charge carrier transport and interface reaction kinetics. The porous nature of the structure can contain the volume expansion of sulfides during cycling, thereby ensuring superior structural stability. The distinctive heterostructure, in combination with the S, N co-doped carbon matrix, enables fast-charge transport and accelerate Na-ion storage kinetics. The SnS/Sb 2 S 3 @SNC anode demonstrates impressive electrochemical performance, with high capacities of 425 mAh g -1 at 200 mA g -1 after 100 cycles, and 302 mAh g -1 at 500 mA g -1 after 400 cycles. Additionally, the SnS/Sb 2 S 3 @SNC anode exhibits remarkable rate capability, with a capacity of over 200 mAh g -1 at a high current density of 5000 mA g -1 . Figure 1