Dimensional Gradient Structure of CoSe2@CNTs-MXene Anode Assisted by Ether for High-Capacity,Stable Sodium Storage

Recently,abundant resources,low-cost sodium-ion batteries are deemed to the new-generation battery in the field of largescale energy storage.Nevertheless,poor active reaction dynamics,dissolution of intermediates and electrolyte matching problems are significant challenges that need to be solved.Herein,dimensional gradient structure of sheet-tube-dots is constructed with CoSe2@CNTs-MXene.Gradient structure is conducive to fast migration of electrons and ions with the association of ether electrolyte.For half-cell,CoSe2@CNTs-MXene exhibits high initial coulomb efficiency(81.7%)and excellent cycling performance(400 mAh g^-1 cycling for 200 times in 2 Ag^−1).Phase transformation pathway from crystalline CoSe2-Na2Se with Co and then amorphous CoSe2 in the discharge/charge process is also explored by in situ X-ray diffraction.Density functional theory study discloses the CoSe2@CNTs-MXene in ether electrolyte system which contributes to stable sodium storage performance owing to the strong adsorption force from hierarchical structure and weak interaction between electrolyte and electrode interface.For full cell,CoSe2@CNTs-MXene//Na3V2(PO4)3/C full battery can also afford a competitively reversible capacity of 280 mAh g^−1 over 50 cycles.Concisely,profiting from dimensional gradient structure and matched electrolyte of CoSe2@CNTs-MXene hold great application potential for stable sodium storage.

Synthesis and photoluminescence kinetics of Ce^(3+)-doped CsPbI3 QDs with near-unity PLQY

CsPbI_(3)perovskite quantum dots(QDs)have great potential in optoelectronic devices due to their suitable band-gaps,but low photoluminescence quantum yields(PLQYs)and poor phase stability seriously impede their practical application.This paper reports the synthesis of Ce^(3+)-doped CsPbI_(3)QDs by a hot injection method.In the presence of the dopant(Ce^(3+)),the highest PLQY of CsPbI_(3)QDs reached 99%,i.e.,near-unity PLQY,and the photoluminescence(PL)emission of CsPbI_(3)QDs could be well maintained compared to that of the undoped ones.The photoluminescence kinetics of Ce^(3+)-doped CsPbI_(3)QDs was investigated by the ultrafast transient absorption technologies,which exhibited that the Ce^(3+)not only increased the density of excitonic states close to the high energy excitonic states(HES),but also provided more emissive channels.Moreover,the radiative recombination rates calculated by the combination of PL lifetime and PLQY further illustrated the Pb2+vacancies were filled with Ce^(3+)ions so that the PL quenching of the CsPbI_(3)QDs could be effectively prevented.The theoretic analysis uncovered the mechanism of the high PLQY and stable PL emission of the Ce^(3+)-doped CsPbI_(3)QDs.