Morphological Evolution of Multilayer Ni/NiO Thin Film Electrodes during Lithiation

Abstract

Oxide conversion reactions in lithium ion batteries are challenged by substantial irreversibility associated with significant volume change during the phase separation of an oxide into lithia and metal species (e.g., NiO + 2Li(+) + 2e(-) → Ni + Li2O). We demonstrate that the confinement of nanometer-scale NiO layers within a Ni/NiO multilayer electrode can direct lithium transport and reactivity, leading to coherent expansion of the multilayer. The morphological changes accompanying lithiation were tracked in real-time by in-operando X-ray reflectivity (XRR) and ex-situ cross-sectional transmission electron microscopy on well-defined periodic Ni/NiO multilayers grown by pulsed-laser deposition. Comparison of pristine and lithiated structures reveals that the nm-thick nickel layers help initiate the conversion process at the interface and then provide an architecture that confines the lithiation to the individual oxide layers. XRR data reveal that the lithiation process starts at the top and progressed through the electrode stack, layer by layer resulting in a purely vertical expansion. Longer term cycling showed significant reversible capacity (∼800 mA h g(-1) after ∼100 cycles), which we attribute to a combination of the intrinsic bulk lithiation capacity of the NiO and additional interfacial lithiation capacity. These observations provide new insight into the role of metal/metal oxide interfaces in controlling lithium ion conversion reactions by defining the relationships between morphological changes and film architecture during reaction.

Facile Preparation of NiO@graphene Nanocomposite with Superior Performances as Anode for Li-ion Batteries

“…Remarkably, NiO is regarded as a promising candidate among TMOs for the favorable theoretical capacity (718 mAh g −1 ), environmental friendliness, low price, natural abundance and safety [12][13][14]. Nevertheless, there are some inevitable weaknesses, such as poor conductivity and large volume changes in pure NiO anodes during the cycling process, which leads to the partial pulverization of electrode materials and the fast decline in capacity [15][16][17]. To overcome these challenges, a variety of nanostructured NiO anode materials, such as nanoparticle [18], nanorod [19], nanosheet [20] and nanotube [21], have been successfully synthesized, and all of them make an outstanding breakthrough in the electrochemical performances.…”

Pulsed Laser Deposition‐based Thin Film Microbatteries

“…A beautiful operando X‐ray reflectometry study was used to probe the function of Ni/NiO multilayer films, these films were sequentially deposited on a Ni substrate and this was placed into an electrochemical cell and cycled while synchrotron X‐ray data were collected, see Figure . Figure shows the comparison of the electron density of the pristine and lithiated states demonstrating dramatic changes in the film during the first lithiation process . Work has also demonstrated the subtle differences in the orientation of films and their evolution during cycling, with 110 oriented films of LiCo 0.2 Ni 0.8 O 2 showing the formation of a thin layer while 003 oriented films only show an increase in surface roughness rather than film formation …”

“…Figure 14 shows the comparison of the electron density of the pristine and lithiated states demonstrating dramatic changes in the film during the first lithiation process. [223] Work has also demonstrated the subtle differences in the orientation of films and their evolution during cycling, with 110 oriented films of LiCo 0.2 Ni 0.8 O 2 showing the formation of a thin layer while 003 Figure 13. Schematic cross-sectional view of a thin film lithium ion battery with charge and discharge capacities as a function of cycle number.…”

“…Calculated densities for the components are shown by the dashed lines. [223] Reprinted with permission from. [223] Copyright 2016 American Chemical Society.…”

“…The electron density profile determined from fits to the reflectometry data showing the pristine (red) and lithiated (green) films. Calculated densities for the components are shown by the dashed lines . Reprinted with permission from .…”