Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange

Abstract

Porous nickel oxide films were deposited onto unheated indium tin oxide coated glass substrates by reactive dc magnetron sputtering. These films had a cubic NiO structure.Electrochromic properties were evaluated in 1 M potassium hydroxide (KOH) and in 1 M lithium perchlorate in propylene carbonate (Li-PC). Large optical modulation was obtained for ~500-nm-thick films both in KOH and in Li-PC (~70 % and ~50 % at 550 nm, respectively). In KOH, tensile and compressive stress, due to expansion and contraction of the lattice, were found for films in their bleached and colored state, respectively. In Li-PC, compressive stress was seen both in colored and bleached films. Durability tests with voltage sweeps between -0.5 to 0.65 V vs Ag/AgCl in KOH showed good durability for 10,000 cycles, whereas voltage sweeps between 2.0 to 4.7 V vs Li/Li + in Li-PC yielded significant degradation after 1000 cycles.

Anodic Electrochromism for Energy‐Efficient Windows: Cation/Anion‐Based Surface Processes and Effects of Crystal Facets in Nickel Oxide Thin Films

“…Our data agree with prior work which has stated several times that the (111) growth direction tends to be favored when Ni oxide films are produced in the presence of a sufficient amount of oxygen [51][52][53] . are consistent with the morphology of our NiO 1.22 films reported on before [30] . The features observed in the SEM images clearly are larger than the grain sizes indicated by XRD and must consist of several grains.…”

“…The electrochromism of lithium-containing Ni oxide films has been investigated in numerous studies aimed at elucidating basic optical and electrochemical mechanisms [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] as well as to produce counter electrodes for application in W-oxide-based EC devices [5,27,32,[34][35][36][37][38] .…”

Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance

“…5b), which can be described in terms of a power law. 22 Clearly, all Ir-Ni oxide films exhibited remarkable electrochemical stability and withstood at least 10,000 CV cycles. Data for films with γ = 4.5% and γ = 5.5% have initial charge densities similar to that for pure Ni oxide, but the decline rate was much smaller.…”

“…[15][16][17][18] Ni oxide was put forward as an alternative 19,20 and has been of sustained interest for almost 30 years. We recently demonstrated that the coloration is a surface process 21 and that the degradation of charge density in Ni oxide obeys a power law 22 upon cycling in a Li-conducting electrolyte, which implies that a monotonic decline of the optical properties takes place and eventually leads to device failure. Many studies during the last years have focused on ways to improve the performance of Ni oxide films with regard to optical modulation speed and span, bleachedstate transmittance and electrochemical cycling durability by use of additives such as Li, [23][24][25] C, 26, 27 N, 28 F, 29 Al, 30 Ti, 31, 32 V, 33,34 Mn, 35 Co, 36 Cu, 37 W, 38,39 (Li,W), 40 (Li,Al), 41 (Li,Zr), 42 and LiPON.…”

The electrochemical cathodic template synthesis of nickel hydroxide thin films for electrochromic devices: role of temperature

“…The following methods are commonly employed in experimental works: pulse laser deposition [11], vacuum sputtering [12], chemical bath deposition [13], sol-gel process [14], spray pyrolysis [15], etc. The main disadvantage of previously listed methods is the difficulty of implementation in the production process of electrochromic devices.…”