Few-Layered Boronic Ester Based Covalent Organic Frameworks/Carbon Nanotube Composites for High-Performance K-Organic Batteries

Abstract

Organic electrodes for low-cost potassium ion batteries (PIBs) are attracting more interest by virtue of their molecular diversity, environmental friendliness, and operation safety. But the sluggish potassium diffusion kinetics, dissolution in organic electrolyte, poor electronic conductivity, and low reversible capacities are several drawbacks compared with inorganic counterparts. Herein, the boronic ester based covalent organic framework (COF) material is successfully prepared on the exterior surface of carbon nanotubes (CNTs) via rational design of the organic condensation reaction and used as an anode material for PIBs. The few-layered structure of COF-10@CNT can provide more exposed active sites and fast K + kinetics. It exhibits ultrahigh potassium storage performances (large reversible capacities of 288 mAh g −1 after 500 cycles at 0.1 A g −1 and 161 mAh g −1 after 4000 cycles at 1 A g −1 ), which is superior to previous organic electrodes and most inorganic electrodes. Moreover, the K-storage mechanism is proposed to be π-cation interaction between K + and conjugated πelectrons of benzene rings.

Covalent Organic Framework Derived Boron/Oxygen Codoped Porous Carbon on CNTs as an Efficient Sulfur Host for Lithium–Sulfur Batteries

“…The galvanostatic intermittent titration technique (GITT) further investigated the dynamic/thermodynamic behavioral characteristics of BOC@CNT/S electrodes (Figure e). From an equation in the previous reports, the D Li+ of two electrodes can be calculated and displayed in Figure f. It is obviously observed that the lithium ion diffusion coefficients for the BOC@CNT/S electrode (1.97 × 10 −9 to 1.36 × 10 −7 cm 2 s −1 ) are higher than those of BOC/CNT/S (2.77 × 10 −11 to 2.22 × 10 −8 cm 2 s −1 ) during the discharging process.…”

Covalent–Organic Frameworks: Advanced Organic Electrode Materials for Rechargeable Batteries

“…[ 22 ] Therefore, Wang and co‐workers proposed a COF‐10@CNT as anode materials for PIBs, where a boronic ester based covalent–organic framework (COF‐10) was in situ grown on the exterior surface of CNTs ( Figure 14 a,b). [ 120 ] Benefiting from its hierarchical pore structure of COF‐10, a sufficient void space was presented to relieve the volume expansion/contraction during potassiation/depotassiation, resulting in a stable performance (Figure 14c). The discharge/charge curves almost overlapped even after 100, 200, 300, 400, and 500 cycles, indicating the stability of electrode structure and excellent reversible electrochemical behaviors (Figure 14c).…”

Metal chalcogenides for potassium storage

“…Inspired by the existing pioneering work involving graphite, tremendous efforts have been devoted to this area of research. To date, several categories of materials are verified to be effective for potassium storage in terms of anodes, including carbon nanophases (eg, hard carbon, graphite, and heteroatom‐doped carbon), alloy‐type (semi‐)metals (eg, Sn, Bi, Sb, and P), metal oxides (eg, Nb 2 O 5 , SnO 2 , Fe x O, and Sb 2 MoO 6 )/sulfides (eg, MoS 2 , VS 2 , SnS 2 , and Sb 2 S 3 ) and phosphides (eg, FeP, CoP, Sn 4 P 3 , and GeP 5 ), sylvite compounds (eg, KVPO 4 F, K 2 V 3 O 8 , KTi 2 (PO 4 ) 3 , and K x Mn y O z ), metal‐organic composites (eg, Co 3 [Co(CN) 6 ] 2 and K 1.81 Ni[Fe(CN) 6 ] 0.97 ·0.086H 2 O), and pure organic polymers (eg, boronic ester, fluorinated covalent triazine, perylene‐tetracarboxylate, perylenetetracarboxylic diimide, azobenzene‐4,4′‐dicarboxylic acid potassium, 2,2′‐azobis[2‐methylpropionitrile], and poly[pyrene‐ co ‐benzothiadiazole]). However, most carbon materials barely deliver reversible capacities exceeding 300 mAh g −1 despite their excellent electrochemical cyclability.…”