Abstract
A new design strategy for high-performance organic cathode active materials for lithium-ion batteries is presented, which involves the assembly of redox-active organic molecules with a crystalline porous structure using mixed-stacked charge-transfer (CT) complexes. Hexahydroxytriphenylene was used as a donor molecule and 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile as an acceptor molecule to give a new porous CT complex (PCT-1) with a pseudo-hexagonal mixed columnar structure. X-ray diffraction measurements and sorption experiments demonstrated that the intercolumnar spaces in PCT-1 can incorporate various molecules accompanied by lattice expansion. A lithium metal battery containing PCT-1 as a cathode active material exhibited a high capacity of 288 mA h g-1 at 500 mA g-1, and this performance was attributed to a combination of the redox-active units and the porous structure of PCT-1.
Highlights
Lithium-ion batteries (LIBs) exhibit a high energy/power density, high performance, and long life.[1,2,3,4] To date, transition metal oxides such as LiMO2 (M 1⁄4 Co, Ni, etc.), LiM2O4 (M 1⁄4 Mn, etc.), and LiMPO4 (M 1⁄4 Fe, Ni, etc.) have been utilized as conventional cathode active materials for LIBs.[5,6] these inorganic materials contain expensive rare elements and/ or exhibit poor rate performance due to the slow intercalation of lithium ions
As the framework of covalent organic frameworks (COFs)-5 is composed of HHTP and boronic acid, and the boronate ester bond undergoes hydrolysis, HHTP molecules are expected to be released gradually under ambient conditions, which could in turn control the nucleation rate of PCT-1$DMF
A lithium metal battery with PCT-1 as a cathode active material exhibited a high capacity and fast charge–discharge properties, which were attributed to the combination of redox-active units and the porous structure of PCT-1
Summary
Lithium-ion batteries (LIBs) exhibit a high energy/power density, high performance, and long life.[1,2,3,4] To date, transition metal oxides such as LiMO2 (M 1⁄4 Co, Ni, etc.), LiM2O4 (M 1⁄4 Mn, etc.), and LiMPO4 (M 1⁄4 Fe, Ni, etc.) have been utilized as conventional cathode active materials for LIBs.[5,6] these inorganic materials contain expensive rare elements and/ or exhibit poor rate performance due to the slow intercalation of lithium ions. Appropriate metal oxide host lattices have been explored to overcome this poor ionic diffusion.[7] Studies on the application of redox-active organic compounds as cathode active materials have become popular due to the high energy/power densities, low cost, diversity, and structural controllability of these compounds.[8,9] Various organic materials such as organosulfur compounds,[10] organic carbonyl compounds,[11,12,13,14,15] tetrathiafulvalene derivatives,[16,17] organic nitrogen compounds,[18,19,20,21] and organic radical compounds[22,23,24] have been examined as potential cathode active materials Since these materials are molecular crystals assembled via weak intermolecular interactions, the formation of robust porous structures is challenging, and instead, densely packed crystal structures in which lithium ions cannot penetrate efficiently are obtained. Most MOFs and COFs contain non-redox-active linker units, such as carboxylates and imines, in their open frameworks, which results in lower energy densities,[36,37] whereas some MOFs and COFs have been designed to include redoxactive linkers.[27,38,39] Despite the high potential of redox-active molecular organic compounds, a universal design strategy for the spontaneous formation of appropriate porous structures for ion diffusion has yet to be discovered to allow the application of such materials as cathode active materials with high rate performance
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
