New electric vehicles and energy storage power stations has put forward high demands for batteries on the energy density and service life.To meet these requirements,extensive efforts have been devoted to exploring new electrode materials with high performance.As an important component of lithium/potassium ion battery,the anode material plays a significant role in determining the performance of the battery.So,developping the anode material with high specific capacity is of great signifitent for lithium/potassium ion battery.Alloying-type and conversion-type electrode materials have high theoretical capacity,while their volume variation severely limits their performance.In addition,the large radius of potassium ions(compared with lithium ions)easily cause the expansion of the active material lattice,resulting in the rapid attenuation of the electrochemical properties.Therefore,resolving the problem of material volume change is important to the development of lithium-ion batteries and potassium ion batteries with high capacity and long cycle life.In this paper,based on the ordered frame materials,such as molecular sieves and metal-organic frame materials(MOFs),we design appropriate nanostructures,improve the stability of electrode surface/interface or prepare the low-strain materials to restrain the serious volume expansion of anodes materials.Moreover,the structure evolution,interface characteristics and energy storage mechanism of the anode materials are studied by the series of characterization methods,electrochemical performance tests and density functional theory(DFT)calculations.These works can provide new ideas to desigin the anode materials with high capacity and long service life.(1)Based on the titanosilicate molecular sieve with the ordered arrangement of[Ti O5]pentahedron and[Si O4]tetrahedron,carbon coated Si O2/Ti O2(Si O2/Ti O2@C)nanosheets are fabricated by ion exchange and heat treatment.The uniform dispersion of Ti O2 particles and its high reaction potential effectively suppress volume deformation of Si O2,maintaining the structural itntegrity during charging/discharging process.Meanwhile,the carbon layer enhances the electronic conductivity and improve the activity of active materials,making the capacity is enhanced by fully reacting the active substance.Under the synergistic effect,Si O2/Ti O2@C nanosheets exhibit an outstanding lithium-storage capability.At the current density of 100 m A g-1,the electrode can remain a reversible capacity of 998 m Ah g-1 after 100 cycles.Even over400 cycles at 2000 m A g-1,it displays an ultrahigh capacity of 410 m Ah g-1.(2)Fe Se/C nanocomposites with Fe Se nanoparticles well confined in carbon matrix are fabricated by an in situ reductive carbonization/selenization of metal organic framework MIL-88B formed by self-assembly between metal ions and organic ligands.This special structure not only inhibits the agglomeration of Fe Se particles,but also improves the electrical conductivity of the material.Besides,by the electrolyte engineering,the potassium storage properties of Fe Se/C in different electrolytes reveal Fe Se/C electrode matches with the KFSI-EC/DEC electrolyte,which significantly boosts the interface stability,relaxes the volume change.Combined with theoretical calculation and electrochemical performance analysis,the solvation structure and physicochemical properties of KFSI-EC/DEC electrolyte jointly regulate the decomposition of the electrolyte,which is crucial to maintaining the stability of the electrode interface and electrode structure.(3)GO-encapsulated on the metal-organic framework(MOF)nanoparticles architecture was synthesized by the formation of Fe-O-C covalent bond in solvothermal synthesis method.After selenization treatment,r GO coated Fe Se/C nanocrystals architecture was constructed.The role of r GO is analyzed from different angles.In addition to the traditional view that r GO is effective in alleviating the volume expansion effect,r GO is very important for the interface behavior of electrolyte.Zate potential analysis and DFT calculation reveal r GO regulated the electrode/electrolyte interface reaction,where the functional groups on the surface of r GO provided favorable conditions for the decomposition of EC and DEC.In addition,r GO promotes electron migration and ion diffusion,and improves the reversibility of the material.As the anode for PIBs,Fe Se/C@r GO exhibited reversible capacity of 197 m Ah g-1 at 1000 m A g-1 after 1900 cycles with ultralow decay rate of 0.086%per cycle,showing excellent ultrastable long cycling performance.(4)To solve volume expansion of electrode for potassium-ion battery,low strain K2Ti2(PO4)3/KTi OPO4 encapsulated in porous carbon substrate(KTP/KTOP/C)composites were synthesized by carbonization/phosphating of MIL-125-NH2.As anode for PIBs,KTP/KTOP/C exhibits high capacity and excellent rate performance.At 1000 m A g-1after 2000cycles,the electrode still remains a reversible capacity of 72 m Ah g-1.Moreover,the electrode maintains the structural integrity,and the volume expansion rate is only 41%.In addition,KTP/KTOP/C anode also shows an excellent electrochemical performance in aluminum current collector,confirming its feasibility in PIBs. |