High-performance Li-organic battery based on thiophene-containing porous organic polymers with different morphology and surface area as the anode materials

Abstract

It is the hot issue for Li-organic battery that whether the higher specific surface area of the porous organic polymers as the electrode materials can benefit to the better battery performance. In this article, the conjugated polymer based on star-shaped benzene-thiophene structure (pBHT) and benzene-ethynyl-thiophene structure (pBAT and pBABT) were designed and successfully prepared. The pBHT polymer exhibits the unique stacked hollow tube morphology and possesses the high surface area (~1139 m2/g), while the polymers pBAT and pBABT both display the macroporous morphology with the low surface area (32.5 m2/g and 12.5 m2/g). Being explored for the battery performance as anode materials, the pBHT electrode exhibits a very low discharge capacity (<100 mAh g−1) and poor cycle’s stability. In contrast, the pBABT electrode with very low surface area of only 12.5 m2/g displays the higher discharge capacity (442 mAh g−1 at 500 mA/g of the second cycle), excellent stability (401 mAh g−1 at 500 mA/g of the 1000 cycles) and higher rate capabilities. These uncommon electrochemical properties may be attributed to the unique hollow tube morphology for the polymer pBHT, which limit the lithium ion released and might form “dead lithium”, thus resulting in the collapse of polymer structures and difficult solid electrolyte interface formation, as well as the fast capacity fading and extremely low capacity according to the electrochemical behaviors and SEM measurements. EIS also confirm the uncommon electrochemical properties with the three polymer electrodes from the kinetics for charge carrier insertion/extraction. Our findings may offer a clue to explore the effect of specific surface area and morphology of polymer electrodes on the performance of LIBs when designing the high-performance electrode materials.