The commercial Li-ion batteries suffer from high cost and severe environmental challenges due to the use of expensive and toxic cobalt-based inorganic materials and the huge amount of CO2 release from the battery material manufacturing and recycling process. To overcome these environmental challenges, the inexpensive, abundant, recyclable, and sustainable polymer materials stand out as promising electrodes for rechargeable batteries. In our work, we demonstrate that the porous polymers are promising cathode materials for rechargeable Na-ion (SIBs), Mg (RMBs) and Al (RABs) batteries. As an example, poly-hexaazatrinaphthalene (PHATN), which is an electron-deficient, rigid and planar aromatic discotic system with pyrazine moieties, enables fast charge/discharge of Na, Mg and Al ions with high cycling stability. PHATN retains reversible capacities of 100 mAh g-1 at 10,000 mA g-1 after 50,000 cycles in SIBs, 110 mAh g-1 at 20 mA g-1 after 200 cycles in RMBs and 92 mAh g-1 at 50 mA g-1 after 100 cycles in RABs. The reaction mechanism for the exceptional rate and cycling performance of PHATN is investigated using density functional theory (DFT), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). For the first time, we prove that imine groups (C=N) in the conjugated polymers can act as the redox centers to reversibly react with Na-ion and multivalent metal ions in the rechargeable batteries. In addition, we also develop a covalent organic framework as a cathode for fast-charge and durable Mg metal batteries. The porous structure of these polymers enables fast reaction kinetics and stable cycle life. Our work demonstrates that the imine group-based porous polymers are promising cathodes for environmentally benign, high-energy-density, fast and stable rechargeable Na-ion and multivalent metal batteries.

Porous polymers for rechargeable Na-ion and multivalent metal batteries

ACS Spring Meeting 2021

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