Layer stacked SiO_(x) microparticle with disconnected interstices enables stable interphase and particle integrity for lithium-ion batteries

Severe mechanical fractu re and unstable interphase,associated with the large volumetric expansion/contraction,significantly hinder the application of high-capacity SiO_(x)materials in lithium-ion batteries.Herein,we report the design and facile synthesis of a layer stacked SiO_(x)microparticle(LS-SiO_(x))material,which presents a stacking structure of SiO_(x)layers with abundant disconnected interstices.This LS-SiO_(x)microparticle can effectively accommodate the volume expansion,while ensuring negligible particle expansion.More importantly,the interstices within SiO_(x)microparticle are disconnected from each other,which efficiently prevent the electrolyte from infiltration into the interior,achieving stable electrode/-electrolyte interface.Accordingly,the LS-SiO_(x)material without any coating delivers ultrahigh average Coulombic efficiency,outstanding cycling stability,and full-cell applicability.Only 6 cycles can attain>99.92%Coulombic efficiency and the capacity retention at 0.05 A g^(-1)for 100 cycles exceeds99%.After 800 cycles at 1 A g^(-1),the thickness swelling of LS-SiO_(x)electrode is as low as 0.87%.Moreover,the full cell with pure LS-SiO_(x)anode exhibits capacity retention of 91.2%after 300 cycles at 0.2 C.This work provides a novel concept and effective approach to rationally design silicon-based and other electrode materials with huge volume variation for electrochemical energy storage applications.

STUDY ON MAXIMUM HYDROGEN CAPACITY FOR Zr-Ni AMORPHOUS ALLOY

To design the amorphous hydrogen storage alloy efficiently, the maximum hydrogen capacities for Zr - Ni amorphous alloy were calculated. Based on the Rhomb Unit Structure Model(RUSM) for amorphous alloy and the experimental result that hydrogen atoms exist in 3Zr1Ni and 4Zr tetrahedron interstices in Zr-Ni amolphous alloy, the numbers of 3Zr-1Ni and 4Zr tetrahedron interstices in a RUSM were calculated which correspond to the hydrogen capacity. The two extremum Zr distribution states were calculated, such as highly heterogeneous Zr distribution and homogeneous Zr distribution. The calculated curves of hydrogen capacity with different Zr contents at two states indicate that the hydrogen capacity increases with increasing Zr content and reaches its maximum when Zr is 75%. The theoretical maximum hydrogen capacity for Zr - Ni amorphous alloy is 2.0 (H/M). Meanwhile, the hydrogen capacity of heterogenous Zr distribution alloy is higher than that of homogenous one at the same Zr content. The experimental results prove the calculated results reasonable, and accordingly, the experimental results that the distribution of Zr atom in amorphous alloy occur heterogeneous after a few hydrogen absorption desorption cycles can be explained.

Small amount but big impact:Trace oxygen interstitially inserted PtCu alloys by microalloying for efficient oxygen reduction catalysis

The introduction of small size non-metal elements(e.g.,oxygen)into solid solution alloys may be a promising strategy for fabricating efficient Pt-based catalysts with high activity and stability toward oxygen reduction reaction(ORR).Herein,oxygen interstitially inserted PtCu(O-PtCu)alloys are firstly designed by an oxygen-microalloying strategy,through ultraviolet(UV)irradiation-assisted galvanic replacement in an aqueous solution containing H_(2)PtCl_(6) and Cu_(2)O nanowires as sacrificial templates.The obtained O-PtCu alloys feature a typical face-centered cubic(FCC)structure with majority Pt,Cu atoms as building bricks and trace interstitial oxygen(1.65 wt.%)existed in the octahedral sites surrounding Cu atoms,leading to a short-range disordered structure.The alloy reaches a recorded half-wave potential of 0.96 V(vs.reversible hydrogen electrode(RHE))and mass activity of 0.48 A·mgPt^(−1),much higher than those of commercial Pt/C.During the accelerated degradation test(ADT),the mass activity lost only 4.2%after 10k cycles,while the commercial Pt/C lost 66.7%under the same conditions.Compared with pure Pt and undoped PtCu alloy,the remarkably improved performance can be attributed to the lattice distortion and energy band reconstruction caused by the interstitial oxygen atoms in form of Cu–O bonds.Moreover,the stable Cu–O bonds delay the possible place exchange between surface Pt atoms and surface-adsorbed oxygen species,thereby hindering Pt dissolution,providing a new paradigm to address Pt degradation issue.Therefore,the introduction of interstitial oxygen into Pt-based alloys may be a facile and smart strategy for the development of advanced Pt-based alloys electrocatalysts.