Deep dive into anionic metal-organic frameworks based quasi-solid-state electrolytes

The development and application of high-capacity energy storage has been crucial to the global transition from fossil fuels to green energy.In this context,metal-organic frameworks(MOFs),with their unique 3D porous structure and tunable chemical functionality,have shown enormous potential as energy storage materials for accommodating or transporting electrochemically active ions.In this perspective,we specifically focus on the current status and prospects of anionic MOF-based quasi-solid-state-electrolytes(anionic MOF-QSSEs)for lithium metal batteries(LMBs).An overview of the definition,design,and properties of anionic MOF-QSSEs is provided,including recent advances in the understanding of their ion transport mechanism.To illustrate the advantages of using anionic MOF-QSSEs as electrolytes for LMBs,a thorough comparison between anionic MOF-QSSEs and other well-studied electrolyte systems is made.With these in-depth understandings,viable techniques for tuning the chemical and topological properties of anionic MOF-QSSEs to increase Li+conductivity are discussed.Beyond modulation of the MOFs matrix,we envisage that solvent and solid-electrolyte interphase design as well as emerging fabrication techniques will aid in the design and practical application of anionic MOF-QSSEs.

Highly Uniform Alkali Doped Cobalt Oxide Derived from Anionic Metal-Organic Framework:Improving Activity and Water Tolerance for CO Oxidation

A sequence of alkali metal cation-exchanged Co metal-organic frameworks(Co-MOFs),therein after denoted as M@Co-MOF,M=Na+,K+,Rb\and Cs+,was prepared and used as the precursors to obtain the corresponding alkali doped cobalt oxide(defined as M/C03O4,M=Na+,K\Rb\and Cs+)through calcination under air atmosphere.The cobalt oxide modified by unifbnn alkali metals exhibited a significant promotion of catalytic activity for CO oxidation.The activity of M/Co3O4 decreased in the order of Cs+>Na+>K+>Rb+.Experimental and theoretical results revealed that the anionic skeleton of Co-MOF could tacilely adsorb alkali metal cations and play a cnicial role in the formation of higlily unilonn alkali doped cobalt oxide.The further characterizations,such as temperature-programmed reduction of H2(H2-TPR),oxygen temperature-programmed desorption(O2-TPD),X-ray photoelectron spectroscopy(XPS),and in situ diffuse reflectance infrared Fourier transiorm(DRIFT)spectra demonstrated that the enlianced catalytic activity is originated from the interfacial electron transfer as well as weakened the Co-O bond strength,which promoted oxygen desorption from CO3O4 and fomiation of cobalt species with the lower valence state.The Cs/Co3O4 catalyst was maintained for 60 h without deactivation and still showed a high activity in the presence of water.

An Anionic Covalent Organic Framework as an Electrostatic Molecular Rectifier for Stabilizing Mg Metal Electrodes

Despite its potential as a high-capacity battery electrode,magnesium(Mg)metals are highly susceptible to electrolytes,resulting in the formation of unwanted passivation layers,which hinder charge transfer phenomena.Here,we first report an anionic covalent organic framework(a-COF)as an electrostatic molecular rectifier(that can preferentially trap solvent molecules)to stabilize Mg metal electrodes.Compared to a neutral COF(n-COF)as a control sample,the a-COF enhances Mg^(2+)transport by facilitating the desolvation of Mg^(2+)-solvent complexes and cationic mobility through its negatively charged one-dimensional columns,thereby achieving an ionic conductivity eight times higher than that of the n-COF.In addition,the anionic porous frameworks in contact with Mg metal electrodes enable a uniform Mg^(2+)flux and interfacial stability with Mg metal electrodes.Consequently,the a-COF exhibited reversible Mg plating/stripping cyclability on Mg metal electrodes compared to the n-COF,demonstrating the electrochemical viability of the anionic frameworks for Mg metal electrode stabilization.