Ordered lithium ion channels of covalent organic frameworks with lithiophilic groups enable uniform and efficient Li plating/stripping

Covalent organic frameworks(COFs)are a kind of materials composed of organic blocks linked through robust covalent bonds[1,2].In these materials,the organic blocks are integrated into symmetric structures that extend infinitely under the guidance of topological diagram,founded by periodic skeletons and nanopores[3-5].On account of the extensive building blocks,variety of topology design diagram and the variety of linkages,various COFs with different functionalities can be designed and synthesized for versatile applications.

Loading Fe3O4 nanoparticles on paper-derived carbon scaffold toward advanced lithium-sulfur batteries

Lithium-sulfur batteries(LSBs) are regarded as a competitive next-generation energy storage device.However, their practical performance is seriously restricted due to the undesired polysulfides shuttling.Herein, a multifunctional interlayer composed of paper-derived carbon(PC) scaffold, Fe3O4 nanoparticles,graphene, and graphite sheets is designed for applications in LSBs. The porous PC skeleton formed by the interweaving long-fibers not only facilitates fast transfer of Li ions and electrons but also provides a physical barrier for the polysulfide shuttling. The secondary Fe3O4@graphene component can reduce the polarization, boost the attachment of polysulfides, and promote the charging-discharging kinetics. The outer graphitic sheets layers benefit the interfacial electrochemistry and the utilization of S-containing species.The efficient obstruction of polysulfides diffusion is further witnessed via in situ ultraviolet-visible characterization and first-principles simulations. When 73% sulfur/commercial acetylene black is used as the cathode, the cell exhibits excellent capacity retention with high capacities at 0.5 C for 1000 cycles and even up to 10 C for 500 cycles, an ultrahigh rate capability up to 10 C(478 m Ah g-1), and a high arealsulfur loading of 8.05 mg cm-2. The strategy paves the way for developing multifunctional composites for LSBs with superior performance.

Fast ion diffusion alloy layer facilitating 3D mesh substrate for dendrite-free zinc-ion hybrid capacitors

Although aqueous zinc ion hybrid capacitors have advantageous integration of batteries and supercapacitors,they still suffer from the inherent problems of dendrite growth and interfacial side reactions on Zn anodes.Herein,a universal fast zinc-ion diffusion layer on a three-dimensional(3 D)mesh structure model is demonstrated to effectively improve Zn plating/stripping reversibility.The fast ion diffusion alloy layer accelerates the Zn^(2+)migration in an orderly manner to homogenize Zn^(2+)flux and overcomes the defects of the commercial mesh substrate,effectively avoiding dendrite growth and side reactions.Consequently,the proof-of-concept silver-zinc alloy modified stainless steel mesh delivers superb reversibility with the high coulombic efficiency over 99.4%at 4 mA cm^(-2)after 1600 cycles and excellent reliability of over 830 h at 1 mA cm^(-2),Its feasibility is also evidenced in commercial zinc ion hybrid capacitors with activated carbon as the cathode.This work enriches the fundamental comprehension of fast zinc-ion diffusion layer combined with a 3 D substrate on the Zn deposition and opens a universal approach to design advanced host for Zn electrodes in zinc ion hybrid capacitors.

Functional-selected LiF-intercalated-graphene enabling ultra-stable lithium sulfur battery

Using a functionally selective solid electrolyte interphase(SEI)as an anodic protection layer can effectively avoid the subsequent settlement of uneven lithium electrodeposits for lithium sulfur(Li-S)batteries.To address the issues of single functional,mechanical crushing and peeling of the conventional rigid LiF SEI,a unique functional-selected rigid-flexible-coupled LiF-intercalated-graphene(LiF-GN)SEI as anodic protection is constructed,which is verified by in-operando X-ray photoelectron spectroscopy(XPS)spectra.Owing to the synergistic effect of the LiF and graphene layer,this intercalated functionalselected SEI architecture exhibits a dramatic elastic modulus(rigid-flexible coupling with a shallow Young’s modulus(~430 MPa)and a tremendous Young’s modulus of~20 GPa),high mechanical strength,and can be repulsive to polysulfides,accompanied unprecedented trafficability of Li ions.Consequently,the forceful exclusion of polysulfides from the LiF-GN SEI,as confirmed by means of in-situ UV/vis analysis,Li2 S nucleation tests,and visual permeation experiments,is of profound significance for the effective protection of Li anodes and enables Li-S batteries to achieve remarkable electrochemical performance(ultralow capacity decay rate of 0.022%during 300 cycles at 1 C and high discharge capacity of 1092 mAh/g at 0.5 C).