Origin of additional capacities in metal oxide lithium-ion battery electrodes

Abstract

Metal fluorides/oxides (MF(x)/M(x)O(y)) are promising electrodes for lithium-ion batteries that operate through conversion reactions. These reactions are associated with much higher energy densities than intercalation reactions. The fluorides/oxides also exhibit additional reversible capacity beyond their theoretical capacity through mechanisms that are still poorly understood, in part owing to the difficulty in characterizing structure at the nanoscale, particularly at buried interfaces. This study employs high-resolution multinuclear/multidimensional solid-state NMR techniques, with in situ synchrotron-based techniques, to study the prototype conversion material RuO2. The experiments, together with theoretical calculations, show that a major contribution to the extra capacity in this system is due to the generation of LiOH and its subsequent reversible reaction with Li to form Li2O and LiH. The research demonstrates a protocol for studying the structure and spatial proximities of nanostructures formed in this system, including the amorphous solid electrolyte interphase that grows on battery electrodes.

Phase evolution for conversion reaction electrodes in lithium-ion batteries

“…The higher capacity relative to the theoretical capacity (718 mAh g À 1 ) suggests that interfacial charge storage and/or reversible side reactions play roles in the extra capacity 22,36 . The reversible side reactions probably include but are not limited to lithium storage in carbon black 37 and CuO 38 at the surface of the Cu current collector, and reversible conversion of LiOH to Li 2 O and LiH 39 . An extraordinary high-rate capability is demonstrated in Fig.…”

In situ methods for Li-ion battery research: A review of recent developments

“…For certain methods this can be achieved with relative ease due to the large similarities in design of their respective in situ cells. Examples of such combinations are: Raman and FTIR [64], XRD and XAS [21], XAS and MS [19], and neutron diffraction together with neutron scattering [106]. Given the recent progress it can be expected that in situ research will become increasingly important in the development of future generations of Li-ion batteries.…”

“…For example, Hu et al [21] unraveled the origin of the additional storage capacity found for nano-sized metal oxide conversion materials by using a combination of in situ XRD, EXAFS and XANES, together with ex situ NMR. Conversion materials, such as a metal oxide (M x O y ), can reversibly react with lithium forming metal particles embedded in a metal oxide matrix, according to…”

Role of anions on structure and pseudocapacitive performance of metal double hydroxides decorated with nitrogen-doped graphene

“…The state-of-the-art material for pseudocapacitors is RuO 2 because of its high conductivity, good capacitance and perfectly reversible chemical reaction, but its high cost and toxic nature impeded its application in real devices [18,19]. Thus, to make pseudocapacitors applicable alternative electrode materials are highly required with fascinating chemical reaction, better conductivity, high © Science China Press and Springer-Verlag Berlin Heidelberg 2015 SCIENCE CHINA Materials ARTICLES stability and capacitance as well as desired values of energy and power densities [20].…”