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

Abstract Terephthalate (C 8 H 4 O 4 2− ) 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 (Li 2 TP) exhibited unsatisfactory cyclic and rate capability. Herein, based on the calculated and experimental results, we demonstrated that potassium terephthalate (K 2 TP) possesses superior cyclic and rate capability in Li-ion batteries. On one hand, due to the larger radius of K + ion, K 2 TP exhibits more stable lattice architecture than Li 2 TP for the better size matching between cations and anions; On the other hand, K + ion in K 2 TP could remain electrochemical inertness even its standard redox potential (−2.931 V) is higher than Li + ion (−3.040 V). Meanwhile, the K O bond in K 2 TP is calculated to be more ionic while the Li O bond in Li 2 TP has more covalent character. The ionic K O bond of K 2 TP 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 K 2 TP anode could exhibit very stable capacity of ∼122 mAh g −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.