A plasma‐enhanced atomic layer deposition (ALD) process is presented, capable of producing thin conformal films of nickel(II) oxide (NiO) on various substrates. Nickelocene (NiCp2) is used as an ...inexpensive metal precursor with oxygen plasma as the oxidant. The film growth rate saturates with both nickel precursor and plasma exposure. An ALD window is observed between 225 and 275 °C. Linear growth is achieved at 250 °C with a growth rate of 0.042 nm per cycle. The thickness is highly uniform and the surface roughness is below 1 nm rms for 52 nm thick films on Si(100). Substrates with aspect ratios up to 1:10 can be processed. As‐deposited, the films consist of polycrystalline, cubic NiO, and are transparent over the entire visible range with an optical bandgap of 3.7 eV. The films consist of stoichiometric NiO and contain ≈1% of carbon impurities. Two promising applications of these films are showcased in renewable energy conversion and storage devices: The films are pinhole‐free and exhibit excellent electron blocking capabilities, making them potential hole‐selective contact layers in solar cells. Also, high electrocatalytic activity of ultrathin NiO films is demonstrated for the alkaline oxygen evolution reaction, especially in electrolytes containing Fe3+.
Plasma‐enhanced atomic layer deposition of transparent crystalline nickel(II) oxide can be used to prepare thin films with great uniformity and control over thickness. The films show very promising electron‐blocking behavior as well as oxygen evolution catalysis in alkaline media, making them attractive for a wide range of renewable energy harvesting and conversion devices.
Transparent conducting films of antimony‐doped tin oxide (ATO) with a uniform 3D mesostructure are prepared by self‐assembly of crystalline ATO nanoparticles directed by commercially available ...Pluronic copolymers. The high electrical conductivity and uniform accessible mesoporosity combined with a simple and generally applicable preparation procedure make the developed ATO films promising nanostructured transparent electrodes for various optoelectronic applications.
The development of high-performance Li 7 La 3 Zr 2 O 12 (LLZO)-based all-solid-state lithium batteries (SSLB) is usually hampered by highly resistive interfaces due to the need for sintering at ...elevated temperatures to form ionic diffusion paths through the grains. Many strategies have been proposed to solve the problem but the achievements have been limited. Herein, a new design principle is introduced, based on co-sintering crystalline LCO and Ta-substituted LLZO instead of using the more reactive Li–Co–O precursors and Al-substituted LLZO, which allows the fabrication of high specific areal density and low cell area resistance without the interface modification of LLZO-based SSLB. Detailed studies using micro-Raman and EDS mapping revealed that the well-sintered interfaces are free from detrimental secondary phases. To demonstrate that a true bulk-type SSLB can be constructed by this straightforward strategy, the material loading for a composite positive electrode was increased to about 10 times that in previous reports, which resulted in a high areal capacity of 1.63 mA h cm −2 ( i.e. 110 mA h g −1 ) when discharged with a current density of 50 μA cm −2 . It also allows one to discharge the fabricated SSLB at a very high current density of 500 μA cm −2 at 50 °C due to the minimized cell areal resistance. The new fabrication strategy for the LLZO-based SSLB paves the way for achieving SSLB with high safety and energy density.
Solid electrolyte is the key component in all-solid-state batteries (ASBs). It is required in electrodes to enhance Li-conductivity and can be directly used as a separator. With its high ...Li-conductivity and chemical stability towards metallic lithium, lithium-stuffed garnet material Li7La3Zr2O12 (LLZO) is considered one of the most promising solid electrolyte materials for high-energy ceramic ASBs. However, in order to obtain high conductivities, rare-earth elements such as tantalum or niobium are used to stabilize the highly conductive cubic phase. This stabilization can also be obtained via high levels of aluminum, reducing the cost of LLZO but also reducing processability and the Li-conductivity. To find the sweet spot for a potential market introduction of garnet-based solid-state batteries, scalable and industrially usable syntheses of LLZO with high processability and good conductivity are indispensable. In this study, four different synthesis methods (solid-state reaction (SSR), solution-assisted solid-state reaction (SASSR), co-precipitation (CP), and spray-drying (SD)) were used and compared for the synthesis of aluminum-substituted LLZO (Al:LLZO, Li6.4Al0.2La3Zr2O12), focusing on electrochemical performance on the one hand and scalability and environmental footprint on the other hand. The synthesis was successful via all four methods, resulting in a Li-ion conductivity of 2.0–3.3 × 10−4 S/cm. By using wet-chemical synthesis methods, the calcination time could be reduced from two calcination steps for 20 h at 850 °C and 1000 °C to only 1 h at 1000 °C for the spray-drying method. We were able to scale the synthesis up to a kg-scale and show the potential of the different synthesis methods for mass production.
On page 6682, D. Leister, M. Stefik, D. Fattakhova‐Rohlfing, and co‐workers describe the fabrication of nanostructured transparent electrodes with remarkably tunable morphologies and adjustable pore ...sizes from 10–80 nm. Porous conducting scaffolds integrate high amounts of photoactive photosystem proteins. This results in greatly increased photocurrents, making them versatile current collectors for the development of bioelectronic devices. Cover image designed by Christoph Hohmann, Nanosystems Initiative Munich (NIM).
We report an original approach for the preparation of quasi two-dimensional graphite sheets by exfoliation of highly oriented pyrolytic graphite. Pieces of HOPG were sonicated for variable time in ...aqueous solutions of phosphomolybdic acid. This leads to a gradual cleavage of the HOPG along the basal plane. The driving force of the process is the free energy resulting from the well-known strong chemisorption of phosphomolybdate ions on carbon. The resulting carbon nanostructures exhibit certain properties of the adsorbed polyoxometalate-anions. They form colloidal suspensions due to the negative surface charge and can be immobilized on surfaces containing cationic groups.
Conducting antimony-doped tin oxide (ATO) nanoparticles are prepared by a nonaqueous solution route, using benzyl alcohol as both the oxygen source and the solvent, and tin tetrachloride and various ...Sb(III) and Sb(V) compounds as tin and antimony sources, respectively. This reaction produces nonagglomerated crystalline particles 3−4 nm in size, which can be easily redispersed in high concentrations in a variety of solvents to form stable transparent colloidal solutions without any stabilizing agents. The synthesis temperature is the most important processing parameter largely governing the reaction course and the particle properties, while the nature of the antimony source has only a marginal influence. The cassiterite SnO2 lattice can accommodate up to 30 mol % antimony without significant changes in the structure. The incorporation of an increasing percentage of antimony causes a continuous decrease in particle size and a slight asymmetric lattice distortion. The introduction of an antimony dopant dramatically increases the particle conductivity, which reaches a maximum for 4% antimony, being more than 2 orders of magnitude higher than that of the pristine SnO2 nanoparticles. The obtained conductivity of 1 × 10−4 S/cm is the highest ever reported for the nonannealed nanosized ATO particles. Annealing in air at 500 °C further improves the conductivity to 2 × 102 S/cm, because of the particle sintering. Exceptionally high conductivity, small size, narrow size distribution, and dispersibility in various organic solvents make the ATO nanoparticles excellent primary building units for assembling nanostructured transparent conducting oxide materials with defined porous architectures.
The increasing demand for safe energy storage has led to intensive investigations of solid-state Li+-ion conductors in the Li2O-M2O3–ZrO2–SiO2–P2O5 system. As a continuation of the cation ...substitution in this system, which we reported on very recently, a study of the impact of polyanionic substitutions on ionic conductivity was carried out here in two series, Li3+xSc2SixP3-xO12 (0 ≤ x ≤ 0.6) and Li1.2+xSc0.2Zr1.8SixP3-xO12 (0.3 ≤ x ≤ 2.8), with the aim of increasing ionic conductivity, determing the phase stability, and optimizing the processing conditions – especially decreasing the sintering temperatures – depending on the level of substitution.The polyanionic substitution, i.e. the substitution of (PO4)3- with (SiO4)4-, in the Li2O–Sc2O3–ZrO2–SiO2–P2O5 system revealed that a) the sintering temperature can effectively be reduced, b) the presence of zirconium can limit the evaporation of lithium species even at high sintering temperatures, c) the purity of the NaSICON materials has a strong influence on the grain boundary resistance, and therefore on the ionic conductivity, and d) the silicate substitution in Li3+xSc2SixP3-xO12 (0 ≤ x ≤ 0.6) stabilized the monoclinic polymorph (space group P21/n) with an enhanced total ionic conductivity at 25 °C from 6.5 × 10−7 S cm−1 to 1.2 × 10−5 S cm−1 for x = 0 to x = 0.15, respectively, exhibiting the highest ionic conductivity at 25 °C among the compositions investigated.
In this article, a versatile process based on microwave‐assisted sol–gel synthesis is introduced in order to apply a surface coating on cathode material for lithium‐ion batteries. Here, a nano‐scaled ...ZnO:Al (AZO) layer is coated homogeneously onto Li(Ni1/3Mn1/3Co1/3)O2 (NMC111) powder at temperatures below 210°C within a few minutes. In contrast to other wet‐chemical coating techniques, the method described here is conducted in a one‐pot reaction and does not require a post‐annealing step at elevated temperatures. Investigations via high resolution transmission electron microscopy (HR‐TEM), scanning transmission electron microscopy (STEM) and inductively‐coupled plasma optical emission spectroscopy (ICP‐OES) promote a thorough understanding of coating microstructure and quality in dependence of reaction temperature, duration and precursor concentration. The AZO protective coating on NMC111 significantly reduces capacity fading during cycling in the voltage range of 3.0‐4.5 V. Furthermore, applying optimal quantities of the coating agent on NMC111 lead to enhanced specific capacities compared to the uncoated material.
A fast, low‐temperature one‐pot process based on microwave‐assisted sol–gel synthesis is utilized to apply nano‐scaled ZnO:Al coatings on Li(Ni1/3Mn1/3Co1/3)O2 cathode powders. Microstructural characterization reveals a high coating homogeneity and surface coverage. Coated cathode material shows improved capacity retention and higher specific capacities compared to uncoated material.
The synthesis of crystalline, nonagglomerated, and perfectly dispersible Co3O4 nanoparticles with an average size of 3–7 nm using a solvothermal reaction in tert‐butanol is reported. The very small ...size and high dispersibility of the Co3O4 nanoparticles allow for their homogeneous deposition on mesoporous hematite layers serving as the photoactive absorber in the light‐driven water splitting reaction. This surface treatment leads to a striking photocurrent increase. While the enhancement of hematite photoanode performance by cobalt oxides is known, the preformation and subsequent application of well‐defined cobalt oxide nanoparticles are novel and allow for the treatment of arbitrarily complex hematite morphologies. Photoelectrochemical and transient absorption spectroscopy studies show that this enhanced performance is due to the suppression of surface electron–hole recombination on time scales of milliseconds to seconds.
Ultrasmall dispersible Co3O4 nanocrystals with an average size of 3–7 nm are prepared by a solvothermal reaction in tert‐butanol. The small size and high dispersibility of the nanoparticles enable their homogeneous deposition on nanostructured Sn‐doped hematite serving as a photoanode in light‐driven water splitting. This surface treatment leads to a striking photocurrent increase.
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