Organicl ithiumi on batteries (LIBs) are considered as one of the next-generation green electrochemical energy storage( EES) devices.H owever,o btaining both high capacity and long-term cyclability is still the bottleneck of organice lectrode materials for LIBs because of weak structural and chemical stability and low conductivity.C ovalento rganic frameworks (COFs) show potential to overcome these problemso wing to its good stabilitya nd high capacity.Herein, the synthesis andc haracterization of two p-conjugated COFs, derived from the Schiff-base reaction of 2,4,6-triaminopyrimidne (TM) respectively with 1,4phthalaldehyde (PA) and1 ,3,5-triformylbenzene( TB) by a mechanochemical process are presented. As anode materials for LIBs, the COFs exhibit favorable electrochemical performance with the highest reversibled ischarge capacities of up to 401.3 and 379.1 mAh g À1 at ah igh current density (1 Ag À1 ), respectively,a nd excellent long-term cyclability with 74.8 and 72.7 %c apacity retention after 2000 cycles compared to the initial discharge capacities.
The further development of conducting polymers (CPs) as electrode materials is restricted by the limited doping level, solely ionic reaction as well as the insufficient reversibility and stability. In order to overcome the deficiency of intrinsic properties, a combined strategy is adopted to modify a p-type CP (polythiophene, PTh) through grafting a radical pendant (2,2,6,6-tetramethylpiperidinyl-1-oxyl, TEMPO) and incorporating a redox-active dopant (Fe(CN) 6 3À ) into the π-conjugated backbone of PTh. TEMPO group works as the electron donor allowing anionic incorporation (PF 6 À , ClO 4 À ) and Fe(CN) 6 3À doping in the conducting matrixes of PTh combines with cations (Li + ) to deliver extra capacity, leading to the final composite shows a successive cationic and anionic (de)intercalation behavior. This dual-ion transportation mechanism of Fe(CN) 6 3À doped P(Th-TEMPO) facilitates the enhanced electrochemical performance, including two significant voltage plateaus (3.6 V and 2.9 V), a reversible capacity from 76 mAh g À 1 to 135 mAh g À 1 at an ultra-high coulombic efficiency (more than 99 %), which result in a high energy density.
We combined a microporous polymer backbone with an organic redox-active dopant to construct a reversible electrode system based on the conversion-(de)incorporation behavior of the dopant. The correspondence between the reversible...
The Cover Feature illustrates the successive cationic and anionic (de)‐intercalation of lithium ions and (de)‐incorporation of PF6−, ClO4− ions for a free‐standing organic electrode. This dual‐ion transportation mechanism of Fe(CN)63− doped P(Th‐TEMPO) facilitates the enhanced electrochemical performance lithium‐ion batteries. More information can be found in the Communication by H. Chen et al.
Polymer-based materials with the incorporation of redox-active dopants serve as promising electrodes for Li-ion batteries but their use is restricted by the limited doping level and inevitable dissolution behavior of the dopants. Here, we proposed a conjugated polymer-based electrode with an assistant dopant to realize the reversible capacity contribution of a redox-active dopant. By employing phosphate anion (PO) as the assistant dopant to stable the polymer matrix, the reversible capacity was improved by introducing indigo carmine (IC) into the polymer electrode. Based on the real-time monitoring of the electrochemical quartz crystal microbalance toward the mass change, the charge storage behavior of the redox-active dopant IC was observed and the stabilizing effect of the assistant dopant PO was revealed. The modified electrode delivered an increased capacity of 191 mA h g −1 , and the reversible capacity remained 56% higher than that of the PO-undoped electrode after 200 cycles. The dual-doping strategy with the assistant dopant and the redox-active dopant is used to develop advanced polymer-based electrodes for high-capacity and long-cycling batteries.
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