Chemically exfoliated few-layer phthalocyanine-based covalent organic frameworks used as improved energy storage electrode for lithium-ion batteries

Covalent organic frameworks (COFs) with abundant redox-active sites are prospective electrode materials for lithium-ion batteries (LIBs). Nevertheless, the sluggish lithium diffusion kinetics, lack of electrical conductivity, and low active point utilization rate of most known covalent organic framework materials limit their further applications. In this work, TACoPc-PDC/MnO 2 composites are synthesized by efficiently exfoliating two-dimensional covalent organic frameworks (TACoPc-PDC) via a strong oxidant intercalation strategy. The in-situ growth of MnO 2 nanoparticles is also realized during the exfoliation process. The MnO 2 nanoparticles are similar to a “spacer”, which allows the TACoPc-PDC to maintain their original few-layer structure in the continuous charging and discharging process, further preventing the re-aggregation of TACoPc-PDC. The prepared TACoPc-PDC/MnO 2 exhibits a less-layered lamellar structure, leaving more active components exposed, which is more favorable for electrochemical performance. Compared with the bulk TACoPc-PDC, the exfoliated TACoPc-PDC exhibits higher capacities, stabler cycling performances, and more outstanding rate capabilities. The initial capacities of the TACoPc-PDC and TACoPc-PDC/MnO 2 electrodes of the LIBs are 194 and 932 mAh/g, respectively, with a current density of 100 mA/g. After the continuous charging and discharging cycling process, the capacities are stabilized at 648 and 1100 mAh/g at 400 cycles. Even at the relatively high current density of 5 A/g, the TACoPc-PDC and TACoPc-PDC/MnO 2 electrodes can realize high specific capacities of 67 and 307 mAh/g. In addition, the cycling stability performance of the electrode materials has been further explored by performing SEM, XRD, and FTIR tests on the electrodes before and after cycling. Therefore, this work fully confirms that the exfoliation strategy using strong oxidant intercalation can provide an effective solution to reduce the aggregation of COFs electrode materials, effectively enhancing the utilization rate of active sites, ultimately achieving prominent energy storage performance.