To
face the challenge of all-climate application, organic rechargeable
batteries must hold the capability of efficiently operating both at
high temperatures (>50 °C) and low temperatures (−20
°C).
However, the low electronic conductivity and high solubility of organic
molecules significantly impede the development in electrochemical
energy storage. This issue can be effectively diminished using functionalized
porphyrin complex-based organic cathodes by the in-situ electropolymerization
of electrodes at elevating temperatures during electrochemical cycling.
[5,15-bis(ethynyl)-10,20-diphenylporphinato]copper(II)
(CuDEPP)- and 5,15-bis(ethynyl)-10,20-diphenylporphinato
(DEPP)-based cathodes are proposed as models, and it is proved that
a largely improved electrochemical performance is observed in both
cathodes at a high operating temperature. Reversible capacities of
249 and 105 mA h g–1 are obtained for the CuDEPP
and DEPP cathodes after 1000 cycles at 50 °C, respectively. The
result indicates that the temperature-induced in situ electropolymerization
strategy responds to the enhanced electrochemical performance. This
study would open new opportunities for developing highly stable organic
cathodes for electrochemical energy storage even at high temperatures.
Organic cathode materials have recently attracted abundant attention due to their flexible structural tunability and recyclability. However, the low intrinsic electrical conductivity and high solubility in electrolytes of organic electrode materials have significantly limited their practical application. Herein, we present [5,15-bis(ethynyl)-10,20-difurylporphinato] copper(II) (Cu-DEOP) as a new cathode for rechargeable organic lithium batteries (ROLBs). The combination of both ethynyl and furyl groups of the CuDEOP cathode with a nanorod structure renders it with enhanced structural stability and an extended delocalized πelectron system to deliver excellent cycling stability (capacity retention of 76% after 6000 cycles) and a high power density (16 kW kg −1 ). The furyl electroactive groups participate in charge storage contribution to achieve a reversible six-electron-transfer redox reaction in a specific voltage range. The mechanism characterizations indicate that the nitrogen atoms on the porphyrin ring act as active sites to alternatively store both PF 6 − anions and Li + cations, and the charge storage process is a pseudocapacitive-dominated reaction. This observation will offer a new avenue for designing functionalized molecules for electrochemical energy-storage (EES) systems.
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