Balanced Crystallinity and Nanostructure for SnS₂Nanosheets 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. SnS₂is 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 SnS₂nanosheets 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.