Hexaazatrinaphthylene-Based Porous Organic Polymers as Organic Cathode Materials for Lithium-Ion Batteries

Abstract

Incorporating small organic molecules with redox-active sites into a suitable porous organic framework could enhance both ion diffusion rate and electronic conductivity while reducing its solubility in electrolytes. Principles for the construction of a redox-active porous organic framework should not sacrifice the theoretical capacity and should balance various important parameters such as specific capacity, cycling stability, rate capability, as well as scalability. Herein, we designed two new porous organic frameworks as cathode materials for lithium-ion batteries (LIBs) using hexaazatrinaphthalene (HATN) cores which show high theoretical capacities. The polymer materials were synthesized in a facile and scalable manner with different structural features ranging from a rigid conjugated framework (HATNPF1) to a flexible nonconjugated framework (HATNPF2). HATNPF polymers demonstrated a high specific capacity (309 mA h g–1), and excellent long-term cycling stability (92% capacity retention after 1200 cycles) and rate capability (65% capacity retention at 2 A g–1 as compared to capacity at 0.2 A g–1), which is an improvement over previously reported porous organic polymers and the HATN monomer. The structure–property relationships of these porous frameworks were also studied using computational modeling.

Conductive Metal–Organic Frameworks with Extra Metallic Sites as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

“…[ 26 ] Since the structure of HATN are extreme controllable, various analogs have been developed as fundamental moieties to fabricate supramolecular systems, especially metallic‐supramolecular frameworks. [ 27–29 ] As a result, HATN may be the optimal structure as a conjugated ligand to fabricate conductive MOFs. In this novel framework, the extra metal atoms, coordinated by bidentate tertamine, can serve as efficient active centers for electrocatalysis, similar to those of single‐atom catalysts.…”

Nitrogen‐Linked Hexaazatrinaphthylene Polymer as Cathode Material in Lithium‐Ion Battery

“…To improve its stability over cycles, efforts such as optimization of the electrolytes or HATN structure and construction of HATN polymers have been reported. Jiang's group developed microporous HATN polymer using 1,4‐(bisethynyl)benzene as linker for lithium‐ion battery applications, which exhibited moderate capacity and cycling stability. Feng reported a nitrogen‐rich sp 2 ‐carbon liked conjugated polymer as cathode with good performance in lithium‐ion batteries .…”

“…Feng reported a nitrogen‐rich sp 2 ‐carbon liked conjugated polymer as cathode with good performance in lithium‐ion batteries . We have also developed a series of HATN porous frameworks linked by a methylene group or sulfur, which exhibit improved capacity and stability …”

“…Hexaazatrinaphthalene (HATN) was first studiedby Sugimoto et al as an organic cathode material (Scheme S1, see the Supporting Information) [16][17][18][19][20][21][22][23][24] with very high theoretical capacity (418 mA h À1 g À1 ). However,c ommond rawbacks of as mallo rganic molecule as cathode material, such as poor cycling stability and high solubility in polar electrolytes,w ere also observed for HATN.…”

“…[24] We have also developed as eries of HATN porousf rameworks linked by am ethylene group or sulfur, which exhibit improved capacity and stability. [21,23] Ad eep understandingo ft he effect al inker has on the electrochemical performance of aH ATNp olymer is crucial for the ensuing polymer design. In general,t he conductivity of polymer material is closely relatedt oi ts HOMO-LUMO gap, [19,21,23] which provides auseful indication for polymer and linker selection.…”