Two Birds One Stone: Graphene Assisted Reaction Kinetics and Ionic Conductivity in Phthalocyanine‐Based Covalent Organic Framework Anodes for Lithium‐ion Batteries

Abstract

AbstractThis work reports a covalent organic framework composite structure (PMDA‐NiPc‐G), incorporating multiple‐active carbonyls and graphene on the basis of the combination of phthalocyanine (NiPc(NH2)4) containing a large π‐conjugated system and pyromellitic dianhydride (PMDA) as the anode of lithium‐ion batteries. Meanwhile, graphene is used as a dispersion medium to reduce the accumulation of bulk covalent organic frameworks (COFs) to obtain COFs with small‐volume and few‐layers, shortening the ion migration path and improving the diffusion rate of lithium ions in the two dimensional (2D) grid layered structure. PMDA‐NiPc‐G showed a lithium‐ion diffusion coefficient (DLi+) of 3.04 × 10−10 cm2 s−1 which is 3.6 times to that of its bulk form (0.84 × 10−10 cm2 s−1). Remarkably, this enables a large reversible capacity of 1290 mAh g−1 can be achieved after 300 cycles and almost no capacity fading in the next 300 cycles at 100 mA g−1. At a high areal capacity loading of ≈3 mAh cm−2, full batteries assembled with LiNi0.8Co0.1Mn0.1O2 (NCM‐811) and LiFePO4 (LFP) cathodes showed 60.2% and 74.7% capacity retention at 1 C for 200 cycles. Astonishingly, the PMDA‐NiPc‐G/NCM‐811 full battery exhibits ≈100% capacity retention after cycling at 0.2 C. Aided by the analysis of kinetic behavior of lithium storage and theoretical calculations, the capacity‐enhancing mechanism and lithium storage mechanism of covalent organic frameworks are revealed. This work may lead to more research on designable, multifunctional COFs for electrochemical energy storage.