Interlayer gap widened TiS_(2) for highly efficient sodium-ion storage

As an alternative for lithium-ion batteries(LIBs),sodium-ion batteries(SIBs)have lately received tremendous interest due to their abundant reserves as well as low cost.Nevertheless,the lack of suitable anode materials severely hinders the application of sodium-ion batteries.TiS_(2)is elected as a representative material owing to its unique layered structure.But it always suffers from capacity fade due to poor electrochemical kinetics and structural stability.In this work,we fabricate a pre-potassiated TiS_(2)as a host material for sodium storage by an electrochemical pre-potassiation strategy.The intercalation/extraction mechanism,structural changes and reaction kinetics are completely investigated to reveal the outstanding electrochemical property of pre-potassiated TiS_(2)electrode.It turns out that the large interlayer space of pre-potassiated TiS_(2)is conducive to the diffusion of sodium ions,inducing the reduction of entropic barrier for the electrochemical reactions.In addition,the pre-potassiated host structure is still firmly maintained upon repeated cycles.Therefore,the pre-potassiated TiS_(2)presents superior rate capability(165.9 mA h g^(−1) at 1 C and 132.1 mA h g^(−1) at 20 C)and long-term cycling stability(85.3%capacity retention at 5 C after 500 cycles)for SIBs.This research provides an avenue to construct long-life sodium energy storage systems based on pre-potassiated TiS_(2).