Balanced Crystallinity and Nanostructure for SnS2 Nanosheets through Optimized Calcination Temperature toward Enhanced Pseudocapacitive Na+ Storage

Sodium ion batteries (SIBs) are expected to take the place of lithium ion batteries (LIBs) as next-generation electrochemical energy storage devices due to the cost advantages they offer. However, due to the larger ion radius, the reaction kinetics of Na+ in anode materials is sluggish. SnS2 is an attractive anode material for SIBs due to its large interlayer spacing and alloying reactions with high capacity. Calcination is usually employed to improve the crystallinity of SnS2, which could affect the Na+ reaction kinetics, especially the pseudocapacitive storage. However, excessively high temperature could damage the well-designed nanostructure of SnS2. In this work, we uniformly grow SnS2 nanosheets on a Zn-, N-, and S-doped carbon skeleton (SnS2@ZnNS). To explore the optimal calcination temperature, SnS2@ZnNS is calcined at three typical temperatures (300, 350, and 400 °C), and the electrochemical performance and Na+ storage kinetics are investigated specifically. The results show that the sample calcined at 350 °C exhibited the best rate capacity and cycle performance, and the reaction kinetics analysis shows that the same sample exhibited a stronger pseudocapacitive response than the other two samples. This improved Na+ storage capability can be attributed to the enhanced crystallinity and the intact nanostructure.