Pre-potassiated hydrated vanadium oxide as cathode for quasi-solid-state zinc-ion battery

Zinc-ion batteries(ZIBs),in particular quasi-solid-state ZIBs,occupy a crucial position in the field of energy storage devices owing to the superiorities of abundant zinc reserve,low cost,high safety and high theoretical capacity of zinc anode.However,as divalent Zn^(2+)ions experience strong electrostatic interactions when intercalating into the cathode materials,which poses challenges to the structural stability and higher demand in Zn^(2+)ions diffusion kinetics of the cathode materials.Here,a microwave-assisted hydrothermal method is adopted to prepare pre-potassiated hydrated vanadium pentoxide(K_(0.52)V_(2)O_(5)·0.29H_(2)O,abbreviated as KHVO)cathode material,in which the potassium ions preinserted into the interlayers can act as“pillars”to stabilize the lamellar structure,and crystal water can act as“lubricant”to improve the diffusion efficiency of Zn^(2+)ions.Consequently,the KHVO displays high electrochemical properties with high capacity(∼300 mAh/g),superior rate capability(69 mAh/g at 5 A/g)and ultralong cycling performance(>1500 cycles at 2 A/g)in quasi-solid-state ZIBs.These superior Zn storage properties result from the large diffusion coefficient and highly stable and reversible Zn^(2+)(de)intercalation reaction of KHVO.

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).