The homogenous growth of Co-based coordination compound on graphene nanosheet for high-performance K-organic battery and its reaction mechanism

Metal coordination compounds(MCCs)are gaining popularity for potassium-ion batteries(PIBs)owing to their tuneable structure,multiple reaction sites,low cost and unique morphology.However,they are generally subjected to intrinsic features of the sluggish ionic diffusion coefficient,low electronic conductivity and slow kinetics.Herein,a new MCC material of cobalt-1,3,5-trioxy-2,4,6-triamino-benzo(Co-TB)coordination compound was synthesized and homogenously grown on the surface of graphene nanosheets(GNS),forming a Co-TB@GNS composite with enhanced electronic conductivity and flexible capability.Benefiting from the overall enhanced conductivity,high surface area and abundant activated K-storage sites,Co-TB@GNS electrodes have exhibited superior cycling performance with high reversible capacities(312 mAh·g^(-1)after 100 cycles at 100 mA·g^(-1),224 mAh·g^(-1)after 500 cycles at 1 A·g^(-1))and better rate performances compared with the pure Co-TB compound when served as PIB's anodes.Furthermore,multiple in-situ measurement techniques have jointly confirmed that the organic functional groups(C=O,C=N and C=C of benzene rings)and Co^(2+)in Co-TB are the main reversible K-storage sites,including in-situ Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD),and partial capacity contribution is originated from GNS by the apparent K-storage behavior in the in-situ XRD pattern,proving the possibility of K-storage for metal-organic materials.