Covalent triazine
frameworks (CTFs) are a class of organic polymer
materials constructed by aromatic 1,3,5-triazine rings with planar
π-conjugation properties. CTFs are highly stable and porous
with N atoms in the frameworks, possessing semiconductive properties;
thus they are widely used in gas adsorption and separation as well
as catalysis. The properties of CTFs strongly depend on the type of
monomers and the synthesis process. Synthesis methods including ionothermal
polymerization, amino-aldehyde synthesis, trifluoromethanesulfonic
acid catalyzed synthesis, and aldehyde–amidine condensation
have been intensively studied in recent years. In this review, we
discuss the recent advances and future developments of CTFs synthesis.
Metal-based materials possess superior electromagnetic interference (EMI) shielding performance because of their extraordinary electrical conductivity. Nevertheless, the high density and structural rigidity of metals seriously limit their applicability in portable and wearable electronic equipment. A common method for reducing the density of metal-based materials is to prepare metal nanowire aerogels by freeze-drying, but the weak connection among the nanowires results in poor mechanical and electrical properties. Herein, a facile approach is developed for the one-step synthesis of silver nanowire (AgNW) aerogels with ultralow density, good flexibility, high electrical conductivity, and a robust structure. The gel is directly formed by in situ assembly of AgNWs. The end-to-end nanojoining of AgNWs contributes to constructing an interconnected three-dimensional (3D) network, resulting in improved mechanical and electrical properties. The AgNW aerogel with an ultralow density of 4.87 mg cm −3 demonstrates a high electrical conductivity of 4584 S m −1 . Moreover, the porous structure of the AgNW aerogel provides numerous interfaces for multiple reflections and scattering of EM waves, allowing them to be continuously absorbed and dissipated within the aerogel. Thus, the AgNW aerogel exhibits a superb EMI shielding effectiveness (SE) of 109.3 dB and a normalized surface specific SE (SSE/t, calculated as the SE divided by the density and thickness) of 353 183 dB cm 2 g −1 , significantly above that of previously known shielding materials. This work provides a new route for preparing high-performance metal nanowire aerogels and their great potential in EMI shielding.
The development of electrolytes with high safety, high
ionic conductivity,
and the ability to inhibit lithium dendrites growth is crucial for
the fabrication of high-energy-density lithium metal batteries. In
this study, a ternary eutectic electrolyte is designed with LiTFSI
(TFSI = bis(trifluoromethanesulfonyl)imide), butyrolactam (BL), and
succinonitrile (SN). This electrolyte exhibits a high ion conductivity,
nonflammability, and a wide electrochemical window. The competitive
solvation effect among SN, BL, and Li+ reduces the viscosity
and improves the stability of the eutectic electrolyte. The preferential
coordination of BL toward Li+ facilitates the formation
of stable solid electrolyte interphase films, leading to homogeneous
and dendrite-free Li plating. As expected, the LiFePO4/Li
cell with this ternary eutectic electrolyte delivers a high capacity
retention of 90% after 500 cycles at 2 C and an average Coulombic
efficiency of 99.8%. Moreover, Ni-rich LiNi0.8Co0.1Al0.1O2/Li and LiNi0.8Co0.1Mn0.1O2/Li cells based on the modified ternary
eutectic electrolyte achieve an outstanding cycling performance. This
study provides insights for understanding and designing better electrolytes
for lithium metal batteries and analogous sodium/potassium metal batteries.
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