Polyoxovanadate ionic crystals with open tunnels stabilized by macrocations for lithium-ion storage
Jie Wang, Lin Wang, Congyan Liu, Yan Wang, Fei Ye, Wen Yan, Бо Лю
Abstract
Polyoxometalates (POMs) with multiple redox active sites have been reported as charge sponge for lithium-ion batteries (LIBs). Herein, we for the first time introduce a polyoxovanadate (POV) ionic crystals with macrocations, [Ni(Phen) 3 ][ClV 14 O34]Cl (NiV 14 , Phen = 1,10-phenanthroline), as an anode material for LIBs. The existence of macrocation [Ni(Phen) 3 ] 2+ stabilizes the open tunnels inside NiV 14 . The NiV 14 electrode exhibits superior rate capabilities (1083 mAh·g −1 at 100 mA·g −1 and 384 mAh·g −1 at 2000 mA·g −1 ) due to the rapid capacitive dominated contribution and high Li + ions diffusion coefficients (3.3 × 10 −12 cm −2 ·s −1 ), and it delivers a remarkable cycling stability with a Coulombic efficiency of 99.7% after 1000 cycles at 2000 mA·g −1 . Such performance can be attributed to the stable structure of NiV 14 and the highly reversible valence changes of vanadium during the charge/discharge processes, which are revealed by a combination of in situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure (XAFS) measurements. This work not only demonstrates that NiV 14 with open tunnels stabilized by macrocation is a promising anode material for high performance LIBs, but also provides important references for the rational design of POMs electrode materials in advanced energy storage systems.