Abstract
Spinel transition metal oxides (TMOs) have emerged as promising anode materials for lithium-ion batteries. It has been shown that reducing their particle size to nanoscale dimensions benefits overall electrochemical performance. Here, we use in situ transmission electron microscopy to probe the lithiation behavior of spinel ZnFe2O4 as a function of particle size. We have found that ZnFe2O4 undergoes an intercalation-to-conversion reaction sequence, with the initial intercalation process being size dependent. Larger ZnFe2O4 particles (40 nm) follow a two-phase intercalation reaction. In contrast, a solid-solution transformation dominates the early stages of discharge when the particle size is about 6–9 nm. Using a thermodynamic analysis, we find that the size-dependent kinetics originate from the interfacial energy between the two phases. Furthermore, the conversion reaction in both large and small particles favors {111} planes and follows a core-shell reaction mode. These results elucidate the intrinsic mechanism that permits fast reaction kinetics in smaller nanoparticles.
Highlights
Spinel transition metal oxides (TMOs) have emerged as promising anode materials for lithium-ion batteries
In order to understand the electrochemical performance of ZFO as a function of particle size, both large and small ZFO were discharged to 0.01 V at a rate of 200 mAg−1
The major difference in the kinetic response of the small ZFO (S-ZFO) and large ZFO (L-ZFO) occurs at the lower depth of discharge (DOD), which is associated with the Li+ intercalation process
Summary
Spinel transition metal oxides (TMOs) have emerged as promising anode materials for lithium-ion batteries. A more recent study found that even when the particles have nanoscale dimensions (
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