Atomic Layer Deposition of NiO to Produce Active Material for Thin-Film Lithium-Ion Batteries

Abstract

Atomic layer deposition (ALD) provides a promising route for depositing uniform thin-film electrodes for Li-ion batteries. In this work, bis(methylcyclopentadienyl) nickel(II) (Ni(MeCp) 2 ) and bis(cyclopentadienyl) nickel(II) (NiCp 2 ) were used as precursors for NiO ALD. Oxygen plasma was used as a counter-reactant. The films were studied by spectroscopic ellipsometry, scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray reflectometry, and X-ray photoelectron spectroscopy. The results show that the optimal temperature for the deposition for NiCp 2 was 200-300 • C, but the optimal Ni(MeCp) 2 growth per ALD cycle was 0.011-0.012 nm for both precursors at 250-300 • C. The films deposited using NiCp 2 and oxygen plasma at 300 • C using optimal ALD condition consisted mainly of stoichiometric polycrystalline NiO with high density (6.6 g/cm 3 ) and low roughness (0.34 nm). However, the films contain carbon impurities. The NiO films (thickness 28-30 nm) deposited on stainless steel showed a specific capacity above 1300 mAh/g, which is significantly more than the theoretical capacity of bulk NiO (718 mAh/g) because it includes the capacity of the NiO film and the pseudo-capacity of the gel-like solid electrolyte interface film. The presence of pseudo-capacity and its increase during cycling is discussed based on a detailed analysis of cyclic voltammograms and charge-discharge curves (U(C)).NiO nanofilms are produced using various methods [12] such as thermal spraying, pulsed laser deposition, sol-gel, spin-coating, dip-coating, chemical vapor deposition, and atomic layer deposition (ALD). ALD is the most promising technology because it provides control over the thickness and purity of coatings with high precision, and can deposit uniform surface coatings on of complex shape and even porous and high aspect ratio substrates [13][14][15]. This method could be a crucial factor for transition from 2D to 3D solid-state batteries (SSB), which are structured on 3D substrates with high aspect ratio instead of planar substrates. It could increase the energy density of SSB with the same thickness of the electrode to maintain the required conductivity of the layers [16]. ALD is based on a realization of the sequence of chemical reactions between gaseous reagents and the surface species of the substrate, separated in time by purges with an inert gas to prevent uncontrolled reactions between the reactants and the reaction products. Because of the self-limiting nature, this method allows the deposition of films in a layer-by-layer fashion and the control of the thickness with high precision [13].When selecting the deposition conditions via ALD, it is necessary to consider the stability and reactivity of the precursors. Many precursors have been tested for ALD NiO so far, but the most frequently used are shown in Table 1: nickel(II) acetylacetonate (Ni(acac) 2 ), bis(2,2,6,6-tetramethylheptane-3,5dionate)nickel(II) (Ni(thd) 2 ), bis(cyclopentadienyl) nickel(II) (NiCp 2 ), and NiCp 2 -based compounds such as ...

Laser-Assisted Synthesis and Oxygen Generation of Nickel Nanoparticles

“…The deconvolution of the Ni2p spectra recorded for NPs placed on the TiO 2 NTs ( Figure 4 c), however, shows more complex surface chemistry, revealing an additional peak doublet. The Ni2p 3/2 peak located at 853.7 eV belongs to NiO, with the Ni2p 3/2 NiO satellite merging with Ni(OH) 2 at approximately 861 eV [ 58 , 60 ]. Based on the proposed deconvolution, the share of the dehydrated NiO in the TiO 2 NTs decorated with NiNPs is around 20%.…”

Growth, physical and electrical characterization of nickel oxide thin films prepared by plasma-enhanced atomic layer deposition using nickelocene and oxygen precursors

“…In terms of the ALD process, the thermal ALD (T-ALD) generally leads to a larger surface roughness (e.g., RMS=0.61.25 nm for 1822 nm NiO films) [2,19,46]; however, our PE-ALD process can attain an improved film roughness, i.e., RMS=0.230.37 nm for 20 nm NiO films, as well as a relatively low deposition temperature (e.g., 225°C). Compared to the reactants of NiCp 2 and O 3 [47], the adoption of NiCp 2 and O 2 -plasma in our case can achieve not only a higher growth rate but also less carbon impurities in the NiO film.…”

Atomic scale surface modification of TiO2 3D nano-arrays: plasma enhanced atomic layer deposition of NiO for photocatalysis

“…, with oxygen plasmas respectively. 9,[20][21][22] These studies have demonstrated that conformal growth of NiO is possible with cyclopentadienyl based nickel precursors and O 2 plasma. Given the low cost of nickelocene (Ni(Cp) 2 ), it should be an attractive precursor for ALD.…”

“…12 %) within deposited films. 22 Here we present a direct-plasma method for the deposition of NiO using the precursor Ni(Cp) 2 , and O 2 plasma, the process was utilised in a new fabrication process for 3D nanostructured arrays, for application in photoelectrochemical water splitting. A systematic investigation has determined that the process is a highly efficient and produced uniform and reproducible NiO with low carbon content.…”