Transition-Metal-Triggered High-Efficiency Lithium Ion Storage via Coordination Interactions with Redox-Active Croconate in One-Dimensional Metal–Organic Anode Materials

Coordination
polymers (CPs) have powerful competence as anode materials for lithium-ion
batteries (LIBs) owing to their structural diversity, tunable functionality,
and facile and mild synthetic conditions. Here, we show that two isostructural
one-dimensional croconate-based CPs, namely, [M­(C5O5)­(H2O)3]n (M = Mn for 1 and Co for 2; C5O52– = croconate dianion), can work
as high-performance electrode materials for rechargeable LIBs. By
means of the coordination between the redox-active transition metal
ion and the ligand, the anode materials were stable in the electrolyte
and showed high capacities, impressive rate capabilities, and excellent
cycling performance during the discharging/charging processes. The
chain-based supramolecular structures of the CPs also make them stand
out from a crowd of porous three-dimensional molecular materials due
to their free channels between the chains for lithium ion diffusion.
When tested in a voltage window of 0.01–2.4 V at 100 mA g–1, CPs 1 and 2 demonstrated
high discharge specific capacities of 729 and 741 mA h g–1, respectively. The synergistical redox reactions on both metal centers
and the organic moieties play a crucial role in the high electrochemical
performance of CPs 1 and 2. After undergoing
elevated discharging/charging rates to 2 A g–1,
the electrodes could finally recover their capabilities as those in
the initial stage when the current rate was back to 100 mA g–1, indicating excellent rate performance and outstanding cycling stabilities
of the materials.