Solvent-Free, Single Lithium-Ion Conducting Covalent Organic Frameworks

Abstract

Porous crystalline materials such as covalent organic frameworks and metal–organic frameworks have garnered considerable attention as promising ion conducting media. However, most of them additionally incorporate lithium salts and/or solvents inside the pores of frameworks, thus failing to realize solid-state single lithium-ion conduction behavior. Herein, we demonstrate a lithium sulfonated covalent organic framework (denoted as TpPa-SO 3 Li) as a new class of solvent-free, single lithium-ion conductors. Benefiting from well-designed directional ion channels, a high number density of lithium-ions, and covalently tethered anion groups, TpPa-SO 3 Li exhibits an ionic conductivity of 2.7 × 10–5 S cm–1 with a lithium-ion transference number of 0.9 at room temperature and an activation energy of 0.18 eV without additionally incorporating lithium salts and organic solvents. Such unusual ion transport phenomena of TpPa-SO 3 Li allow reversible and stable lithium plating/stripping on lithium metal electrodes, demonstrating its potential use for lithium metal electrodes.

Transformation between 2D and 3D Covalent Organic Frameworks via Reversible [2 + 2] Cycloaddition

“…These values are several orders magnitude faster than in LiClO4 hydrate (T1 = 77.5 ± 0.2 s at ~40% RH; even longer recovery time ~2.510 3 s was reported 51 for anhydrous LiClO4) and are among the fastest reported for Li-impregnated COFs. 51,53 The lithium ion conductivity of P 2 PV and P 3 PcB COFs was measured using electrochemical impedance spectroscopy on compressed pellets impregnated with LiClO4 (30% w/w), at room temperature (297 K) and RH of ~40%. The fit of the Nyquist plots reveals a notable room-temperature ionic conductivity of ~1.8×10 −4 S/cm and ~3.5 × 10 −5 S/cm for P 2 PV and P 3 PcB, respectively (Figure 9a).…”

Crystalline Anionic Germanate Covalent Organic Framework for High CO2 Selectivity and Fast Li Ion Conduction

“…Recently,i onic covalent organic frameworks are envisioned as Li-ion conducting solid electrolytes due to its lightweighta nd highly tunable pore structure.M ost of the pristine ionic covalento rganic framework has an egligible conduction of lithium ions at room temperature, except a recently reported lithium sulfonated covalento rganic framework with ac onductivity of 2.7 10 À5 Scm À1 . [9] There are two extrinsicm ethods to improvet he conductivity of covalent organic frameworks:i nfiltration with as mall amount of high dielectric constant solventa nd/or lithium salt. [2e,h,i, 10a,b-e] Another plausible wayt oi mprovet he ion conductivity is to introduce heavier and soft elements, [11] whichw as demonstrated by inorganic solid electrolytes such as substitution of Si by Ge in phosphidosilicates ([SiP 4 ] 8À )t op hosphidogermanates ([GeP 4 ] 8À ), [12] changeo fC lt oB ri ny ttrium halides ([YCl 6 ] 3À )t o ([YBr 6 ] 3À ).…”

A single-ion conducting covalent organic framework for aqueous rechargeable Zn-ion batteries

“…TpPa-SO 3 Zn 0.5 was synthesised via the solvothermal reaction of 1,3,5-triformylphloroglucinol (Tp) and 1,4-phenylenediamine-2sulfonic acid (Pa-SO 3 H) to obtain a sulfonic acid COF (TpPa-SO 3 H; yield: 96%), 28,34 followed by reaction with zinc acetate to exchange H + with Zn 2+ (yield: 91%; Scheme S1 †). The CHN analysis and inductively coupled plasma optical emission spectrometry (ICP-OES) results show that the elemental composition of the synthesised TpPa-SO 3 Zn 0.5 matches well with the theoretical composition (e.g., for the Zn content, 10.09 (calcd.)…”

“…COFs have been regarded as appealing ion transport media owing to their ordered porous structure, functionalities and structural stability. [27][28][29][30][31][32][33] A zinc sulfonated COF (TpPa-SO 3 Zn 0.5 ; Fig. 1a) is synthesised to build well-dened directional channels in which covalently tethered and delocalised sulfonates play key roles in realising single Zn 2+ transport.…”