Principles of interlayer-spacing regulation of layered vanadium phosphates for superior zinc-ion batteries

Layered vanadium phosphate (VOPO4 center dot 2H(2)O) is reported as a promising cathode material for rechargeable aqueous Zn2+ batteries (ZIBs) owing to its unique layered framework and high discharge plateau. However, its sluggish Zn2+ diffusion kinetics, low specific capacity and poor electrochemical stability remain major issues in battery application. In this work, a group of phenylamine (PA)-intercalated VOPO4 center dot 2H(2)O materials with varied interlayer spacing (14.8, 15.6 and 16.5 angstrom) is synthesized respectively via a solvothermal method for the cathode of aqueous ZIBs. The specific capacity is quite dependent on the d-spacing in the PA-VOPO4 center dot 2H(2)O system following an approximate linear tendency, and the maximum interlayer spacing (16.5 angstrom phase) results in a discharge capacity of 268.2 mA h g(-1) at 0.1 A g(-1) with a high discharge plateau of similar to 1.3 V and an energy density of 328.5 W h kg(-1). Both of the experimental data and DFT calculation identify that the optimal 16.5 angstrom spacing can boost fast zinc-ion diffusion with an ultrahigh diffusion coefficient of similar to 5.7 x 10(-8) cm(-2) s(-1). The intercalation of PA molecules also significantly increases the hydrophobility in the aqueous electrolyte, resulting in the inhibition of the decomposition/dissolution of VOPO4 center dot 2H(2)O and remarkably improved cycling stability over 2000 cycles at 5.0 A g(-1) with a capacity retention of similar to 200 mA h g(-1). Our study provides a feasible solution for the sluggish Zn2+ diffusion kinetics and poor cyclic stability, and also shows a clear understanding of the interlayer chemistry principle of layered phosphates toward high-performance zinc-ion batteries.