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

• Published in: Electrochimica acta 2016-12, Vol.222, p.1086-1093
• Main Authors: Deng, Qijiu, Fan, Cong, Wang, Liping, Cao, Bei, Jin, Yingdi, Che, Chi-Ming, Li, Jingze
• Format: Article
• Language: English
• Subjects: Cyclic and rate capability; Lattice stability; Li-ion batteries; Organic anode; Potassium terephthalate
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2016.11.079

Potassium terephthalate possesses superior rate and cyclic capability in Li-ion batteries due to the electrochemically stable terephthalate moiety as well as its excellent lattice stability. The modified potassium terephthalate anode could exhibit the remarkably stable capacity of ∼122mAhg−1 at the current rate of 8C for 500 cycles. [Display omitted] •Potassium terephthalate (K2TP) has more stable crystal structure.•K2TP exhibits superior rate and cyclic capability in Li-ion batteries.•Very stable capacity of ∼122mAhg−1 at 8C is maintained for 500 cycles. 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.