Organic Potassium Terephthalate (K2C8H4O4) with Stable Lattice Structure Exhibits Excellent Cyclic and Rate Capability in Li-ion Batteries

Abstract

Terephthalate (C8H4O42−) moiety with stable oxidized and reduced states is widely employed as the organic anode in batteries. However, along with the dissolution problem, the representative lithium terephthalate (Li2TP) exhibited unsatisfactory cyclic and rate capability. Herein, based on the calculated and experimental results, we demonstrated that potassium terephthalate (K2TP) possesses superior cyclic and rate capability in Li-ion batteries. On one hand, due to the larger radius of K+ ion, K2TP exhibits more stable lattice architecture than Li2TP for the better size matching between cations and anions; On the other hand, K+ ion in K2TP could remain electrochemical inertness even its standard redox potential (−2.931V) is higher than Li+ ion (−3.040V). Meanwhile, the KO bond in K2TP is calculated to be more ionic while the LiO bond in Li2TP has more covalent character. The ionic KO bond of K2TP could further enhance its dissolution resistance against non-polar electrolyte. Indeed, after its electronic conductivity and particle dispersity were improved by mixing with graphene, the modified K2TP anode could exhibit very stable capacity of ∼122mAhg−1 at 8C for 500 cycles, which is comparable or even superior to the state-of-the-art Li-ion batteries currently reported for small organic molecules.