GeO₂ Thin Film Deposition on Graphene Oxide by the Hydrogen Peroxide Route: Evaluation for Lithium-Ion Battery Anode

Abstract

A peroxogermanate thin film was deposited in high yield at room temperature on graphene oxide (GO) from peroxogermanate sols. The deposition of the peroxo-precursor onto GO and the transformations to amorphous GeO, crystalline tetragonal GeO, and then to cubic elemental germanium were followed by electron microscopy, XRD, and XPS. All of these transformations are influenced by the GO support. The initial deposition is explained in view of the sol composition and the presence of GO, and the different thermal transformations are explained by reactions with the graphene support acting as a reducing agent. As a test case, the evaluation of the different materials as lithium ion battery anodes was carried out revealing that the best performance is obtained by amorphous germanium oxide@GO with >1000 mAh g at 250 mA g (between 0 and 2.5 V vs Li/Li cathode), despite the fact that the material contained only 51 wt % germanium. This is the first demonstration of the peroxide route to produce peroxogermanate thin films and thereby supported germanium and germanium oxide coatings. The advantages of the process over alternative methodologies are discussed.

Doubly Coated, Organic–Inorganic Paraffin Phase Change Materials: Zinc Oxide Coating of Hermetically Encapsulated Paraffins

“…We stipulated that hydrogen peroxide sol–gel processing is an alternative coating pathway that should be explored, though, as outlined below, its application to coating of microencapsulated materials was less straightforward than anticipated. Hydroperoxo ligands stabilize d‐10 and p‐block element oxide and peroxide nanoparticles in aqueous solution (at moderate pH), and the resulting sol can be deposited on microparticulates by mild destabilization (vide infra) …”

Are Electrospun Fibrous Membranes Relevant Electrode Materials for Li‐Ion Batteries? The Case of the C/Ge/GeO2 Composite Fibers

“…In the latest years, several studies have been conducted on electrode materials based on germanium and the cheaper germanium dioxide (GeO 2 ) . In GeO 2 , Li storage occurs via a conversion reaction leading to the irreversible formation of Li 2 O, which lowers down to 1126 mAh g −1 the gravimetric capacity attainable in the subsequent alloying reaction.…”

“…Very recently, Seng et al have pointed out the catalytic role played by elemental Ge NPs in the GeO 2 /Ge/C nanocomposites, having beneficial effects on the reversibility of the conversion reaction of GeO 2 . For these reasons, several Ge, GeO 2 , and Ge/GeO 2 ‐based composites containing graphene or reduced graphene oxide, carbon and nitrogen‐doped carbon nanofibers, or other forms of carbon have been evaluated as anode materials.…”

“…However, only a few of them are binder‐free electrode materials . Being in the form of powders, the most of them cannot be directly utilized as anodes, and the electrode is prepared by using a limited amount of the active material (even only 60−70 wt%) together with binder and conductive additive . The incorporation of extra substances results in a “dilution” of the lithium storage performance in terms of gravimetric, areal, and volumetric capacities …”

“…In addition, most of these studies are focused on one composite electrode material, prepared under fixed conditions, and compare its electrochemical behavior to that of commercial references and/or of its single components . Only in a few studies different preparation conditions are evaluated . This prevents to draw clear structure–properties correlations, and to evaluate the effect caused by the change of any synthesis parameter.…”