Structure and LIBs Anode Material Application of Novel Wells–Dawson Polyoxometalate-Based Metal Organic Frameworks with Different Helical Channels

Two new Wells–Dawson polyoxometalate-based metal–organic frameworks (POMOFs) with different helical channels were synthesized depending on the self-adaptive coordination nature of P2W18 polyanion. The hemispherical coordination of P2W18 clusters with Ag under the help of 1,2,4-triazole ligand induces the isolation of the twofold helical channels-containing POMOF 1, while the clockwise coordination of P2W18 clusters with Cu results in the fourfold helical channels-containing POMOF 2. Both compounds exhibit good electrochemical performance as lithium-ion batteries electrode materials due to their excellent redox properties and structural stabilization. The long-term cycling capacity as demonstrated by the still above 400–450 mA h g–1 for 350 cycles at the current density of 100 mA g–1 reveals the important role of the helical channels within exposed P2W18 polyanions in 1 and 2, which allow the relatively easy Li+ deintercalation/intercalation. To illustrate the lithium storage, the impedance spectra of compound 2 during the first and 350th charge process was also studied for the first time.