Abstract
The stress inevitably imposed during electrochemical reactions is expected to fundamentally affect the electrochemistry, phase behavior and morphology of electrodes in service. Here, we show a strong stress-composition coupling in lithium binary alloys during the lithiation of tin-tin oxide core-shell nanoparticles. Using in situ graphene liquid cell electron microscopy imaging, we visualise the generation of a non-uniform composition field in the nanoparticles during lithiation. Stress models based on density functional theory calculations show that the composition gradient is proportional to the applied stress. Based on this coupling, we demonstrate that we can directionally control the lithium distribution by applying different stresses to lithium alloy materials. Our results provide insights into stress-lithium electrochemistry coupling at the nanoscale and suggest potential applications of lithium alloy nanoparticles.
Highlights
The stress inevitably imposed during electrochemical reactions is expected to fundamentally affect the electrochemistry, phase behavior and morphology of electrodes in service
In addition to causing electrode cracking, stress couples to the insertion electrochemistry, affecting the electrode potential, lithiation kinetics, and Li composition[8,9]. These electrochemistry–stress couplings have been studied in depth, including the stress contribution to chemical potential[10] or stress-induced kinetic retardation[11,12]
Since the compositional spatiodynamics in battery materials occurs on a nanoscale, nanoscale observations are essential[15]. Realizing this capability has been challenging with the current state-of-theart characterization techniques such as in situ transmission electron microscopy (TEM) on an encapsulated liquid[16]
Summary
The stress inevitably imposed during electrochemical reactions is expected to fundamentally affect the electrochemistry, phase behavior and morphology of electrodes in service. We show a strong stress-composition coupling in lithium binary alloys during the lithiation of tin-tin oxide core-shell nanoparticles. Our results provide insights into stress-lithium electrochemistry coupling at the nanoscale and suggest potential applications of lithium alloy nanoparticles. In addition to causing electrode cracking, stress couples to the insertion electrochemistry, affecting the electrode potential, lithiation kinetics, and Li composition[8,9]. Since the compositional spatiodynamics in battery materials occurs on a nanoscale, nanoscale observations are essential[15] Realizing this capability has been challenging with the current state-of-theart characterization techniques such as in situ transmission electron microscopy (TEM) on an encapsulated liquid[16]. Here, we use in situ graphene liquid cell electron microscopy (in situ GLC-EM)[17,18] to visibly track the temporal phase and morphological evolution of a single nanoparticle while it lithiates under stress. Owing to its relatively low alloying energy of −0.48 eV, Li3.5Sn is a suitable material for studying the interaction between electrochemistry and stress, which occurs on a comparable energy scale
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