The impact of size effects on the electrochemical behaviour of Cu2O-coated Cu nanopillars for advanced Li-ion microbatteries

Abstract

The generation of a distribution of nanoparticles upon conversion reaction of thin Cu 2 O layers is demonstrated to produce a wide electrochemical potential window, as well as a distinctive capacity increase in large area three-dimensional electrodes. Cu nanopillars with a 10-15 nm Cu 2 O coating containing traces of nanocrystalline Fe 2 O 3 yield capacities up to 0.265 mA h cm À2 (at 61 mA g À1 ), excellent cycling for more than 300 cycles and an electroactive potential window larger than 2 V, due to the size effects caused by the various Cu/Cu 2 O nanoparticles formed during conversion/deconversion. These 3D Li-ion battery electrodes based on electrodeposited Cu nanopillars spontaneously coated with a Cu 2 O layer are compatible with current densities of 16 A g À1 (i.e. 61 C rates) after aerosol-assisted infiltration with an iron acetate solution followed by low-temperature pyrolysis. The capacity of the composite material increases by 67% during 390 cycles due to the growth of the electroactive area during the electrochemical milling of Cu 2 O forced by its repeated conversion/de-conversion. The latter generates a distribution of nanoparticles with different sizes and redox potentials, which explains the broad potential window, as well as the significant capacity contribution from double layer charging.These 3D electrodes should be well-suited for Li-ion microbatteries and Li-ion batteries in general, since they combine high capacities per footprint area with excellent power capabilities. More importantly, such electrodes grant access to fundamental understanding of the electrochemical behaviour of these active materials providing new insights into both conversion mechanisms and nanostructured interfaces more in general.

MOF derived porous carbon supported Cu/Cu 2 O composite as high performance non-noble catalyst

“…3A) [6,20,21]. For Cu/Cu 2 O/C, the main peaks at 932.7 eV and 934.7 eV were assigned to Cu 2 O and/or Cu and Cu(OH) 2 , respectively [21,22], whereas the shake-up peaks at 941.3 eV and 944.2 eV were ascribed to Cu(OH) 2 , which is often found for atmosphere-exposed Cu 2 O surfaces [22,23]. The O1s spectrum of HKUST-1 (Fig.…”

Latest advances in the manufacturing of 3D rechargeable lithium microbatteries

“…A common strategy is the growth of metal pillars used as current collectors followed by the deposition of the active material on them. For example K. Edström's group developed a method to deposit TiO2 using ALD on Al nanorods [53] and CuO2 via electrodeposition on Cu nanopillars, showing in this latter case that CuO2, which undergoes a conversion reaction, can work well when directly wired to an underlying 3D Cu current collector [42,54].…”

Hierarchical self-assembled structures based on nitrogen-doped carbon nanotubes as advanced negative electrodes for Li-ion batteries and 3D microbatteries

“…1.62 V vs. Li þ /Li), are associated to a size distribution of the hematite nanostructures. The latter undergo electrochemical milling upon progressive conversion and de-conversion, thus generating a broad range of reaction potentials for the differently sized nanostructures [3]. The impact of these size effects on the electrochemical activity of the hierarchical HR/NCNTs/CP structures is evident in Fig.…”

“…In fact, the enhanced double layer charging in these cycles at increasing scan rates is clearly noticed, when compared to those analogously obtained for the NCNTs/CP and blank CP electrodes. The electrochemical response of the hematite nanostructures becomes more pronounced at higher scan rates, thus implying a more efficient charge storage combining both double layer charging and faradaic reactions over a broad range of potentials [3].…”

“…This raises the energy density of the entire electrode assembly, while retaining the beneficial characteristics of the nanostructured materials and their extended interfaces. 3D electrodes have thus the potential to address the main issues of conventional planar configurations, provided that a suitable matching of the materials ensures a good adhesion between the conductive network and the active component(s), without negating porosity and a quick access to both Li þ and e À through the entire structure [3,9]. These characteristics are crucial, especially if miniaturizing the entire battery would impose further limitations on the available space for its various components, which would need to be downscaled as well [2,9].…”