Efficient Polytelluride Anchoring for Ultralong-Life Potassium Storage: Combined Physical Barrier and Chemisorption in Nanogrid-in-Nanofiber

Metal tellurides(MTes) are highly attractive as promising anodes for high-performance potassium-ion batteries. The capacity attenuation of most reported MTe anodes is attributed to their poor electrical conductivity and large volume variation. The evolution mechanisms, dissolution properties, and corresponding manipulation strategies of intermediates(K-polytellurides, K-pTe_(x)) are rarely mentioned. Herein,we propose a novel structural engineering strategy to confine ultrafine CoTe_(2) nanodots in hierarchical nanogrid-in-nanofiber carbon substrates(CoTe_(2)@NC@NSPCNFs) for smooth immobilization of K-pTe_(x) and highly reversible conversion of CoTe_(2) by manipulating the intense electrochemical reaction process. Various in situ/ex situ techniques and density functional theory calculations have been performed to clarify the formation, transformation, and dissolution of K-pTe_(x)(K_(5)Te_(3) and K_(2)Te), as well as verifying the robust physical barrier and the strong chemisorption of K_(5)Te_(3) and K_(2)Te on S, N co-doped dual-type carbon substrates. Additionally, the hierarchical nanogrid-in-nanofiber nanostructure increases the chemical anchoring sites for K-pTe_(x), provides sufficient volume buffer space, and constructs highly interconnected conductive microcircuits, further propelling the battery reaction to new heights(3500 cycles at 2.0 A g^(-1)). Furthermore, the full cells further demonstrate the potential for practical applications. This work provides new insights into manipulating K-pTe_(x) in the design of ultralong-cycling MTe anodes for advanced PIBs.

Enhanced thermoelectric performance of two dimensional MS2(M=Mo,W)through phase engineering

The potential application of monolayer MS2(M?Mo,W)as thermoelectric material has been widely studied since the first report of successful fabrication.However,their performances are hindered by the considerable band gap and the large lattice thermal conductivity in the pristine 2H phase.Recent discoveries of polymorphism in MS2s provide new opportunities for materials engineering.In this work,phonon and electron transport properties of both 2H and 1T0 phases were investigated by first-principle calculations.It is found that upon the phase transition from 2H to 1T0 in MS2,the electron transport is greatly enhanced,while the lattice thermal conductivity is reduced by several times.These features lead to a significant enhancement of power factor by one order of magnitude in MoS2 and by three times in WS2.Meanwhile,the figure of merit can reach up to 0.33 for 1T0eMoS2 and 0.68 for 1T0eWS2 at low temperature.These findings indicate that monolayer MS2 in the 1T0 phase can be promising materials for thermoelectric devices application.Meanwhile,this work demonstrates that phase engineering techniques can bring in one important control parameter in materials design.