Tuning the electronic energy level of covalent organic frameworks for crafting high-rate Na-ion battery anode

Abstract

<p>Lowering the LUMO levels of an anodic COF through the incorporation of N-rich modules favors electron accumulation on it, which sets up an electronic drive for the Na⁺ ions to enter the anode from the electrolyte. The optimal framework⋯Na⁺ interactions delivers excellent rate-performance.</p>

Covalent Organic Frameworks for Batteries

“…Vaidhyanathan and coworkers unraveled the relationship between molecular‐level electronic structure and SIB performance. [ 154 ] The band gaps of COFs were tuned through the introduction of heteroatom N in the COF structures. They found that COFs with lower lowest unoccupied molecular orbital (LUMO) levels enabled easier electron accumulations and outperformed other COFs with higher LUMO levels.…”

Advances in electrochemical energy storage with covalent organic frameworks

“…Using a similar strategy, Vaidyanathan's group implanted multiple N heteroatoms into β-ketoenaminelinked COFs to adjust their electronic energy levels. 115 These COFs, IISERP-COF16, -17, and -18, contained terphenyl spacers, s-tetrazine units, and s-tetrazine bispyridine units, respectively. The lowest unoccupied molecular orbital (LUMO) energy of IISERP-COF18 was estimated as −4.31 eV, which was lower than that of IISERP-COF16 (−3.75 eV) owing to its high N content.…”

Covalent Organic Frameworks as Electrode Materials for Rechargeable Batteries

“…IISERP-COF16, IISERP-COF17, and IISERP-COF18 were synthesized containing phenyl, tetrazine, and bispyridine-tetrazine moieties, respectively, in efforts to drive Na-ions into their pores via favorable interactions (Figure 24a). 85 CVs were used to investigate the sodiation/desodiation mechanisms within a potential window of 0.05-3 V (Figure 24c). For IISERP-COF17 and IISERP-COF18, the sodium insertion during the discharge occurred via a two-step process (Figure 24b).…”