Synthesis of nanostructured LiMn2O4 thin films by glancing angle deposition for Li-ion battery applications

Glancing angle deposition of large-scale helical Si@Cu3Si nanorod arrays for high-performance anodes in rechargeable Li-ion batteries

Silicon (Si) anode materials have attracted substantial interest due to their high theoretical capacity. Here, the growth of helical Si@Cu₃Si nanorod arrays via glancing angle deposition (GLAD) followed by an annealing process is reported. Pre-deposited Cu atoms were driven into Si-nanorods and successfully reacted with Si to form a Si-Cu alloy at a high temperature. By varying the rotation rate and annealing temperature, the resultant Si@Cu₃Si nanorod arrays showed a reasonably accessible surface area with precise control spacing behavior in favor of accommodating Si volume expansion. Meanwhile, the Si@Cu₃Si anode materials showed higher electrical conductivity, facilitating Li⁺ ion diffusion and electron transfer. The Si@Cu₃Si nanorod arrays in half cells exhibited a volumetric capacity as high as 3350.1 mA h cm^-3 at a rate of 0.25 C and could maintain 1706.7 mA h cm^-3 after 100 cycles, which are superior to those of pristine Si materials. This facile and innovative technology provided new insights into the development of Si-based electrode materials.

Physical Vapor Deposition in Solid-State Battery Development: From Materials to Devices

This review discusses the contribution of physical vapor deposition (PVD) processes to the development of electrochemical energy storage systems with emphasis on solid-state batteries. A brief overview of different PVD technologies and details highlighting the utility of PVD for the fabrication and characterization of individual battery materials are provided. In this context, the key methods that have been developed for the fabrication of solid electrolytes and active electrode materials with well-defined properties are described, and demonstrations of how these techniques facilitate the in-depth understanding of fundamental material properties and interfacial phenomena as well as the development of new materials are provided. Beyond the discussion of single components and interfaces, the progress on the device scale is also presented. State-of-the-art solid-state batteries, both academic and commercial types, are assessed in view of energy and power density as well as long-term stability. Finally, recent efforts to improve the power and energy density through the development of 3D-structured cells and the investigation of bulk cells are discussed.

Electrochemical Methods for Lithium Recovery: A Comprehensive and Critical Review

Due to the ubiquitous presence of lithium-ion batteries in portable applications, and their implementation in the transportation and large-scale energy sectors, the future cost and availability of lithium is currently under debate. Lithium demand is expected to grow in the near future, up to 900 ktons per year in 2025. Lithium utilization would depend on a strong increase in production. However, the currently most extended lithium extraction method, the lime-soda evaporation process, requires a period of time in the range of 1-2 years and depends on weather conditions. The actual global production of lithium by this technology will soon be far exceeded by market demand. Alternative production methods have recently attracted great attention. Among them, electrochemical lithium recovery, based on electrochemical ion-pumping technology, offers higher capacity production, it does not require the use of chemicals for the regeneration of the materials, reduces the consumption of water and the production of chemical wastes, and allows the production rate to be controlled, attending to the market demand. Here, this technology is analyzed with a special focus on the methodology, materials employed, and reactor designs. The state-of-the-art is reevaluated from a critical perspective and the viability of the different proposed methodologies analyzed.

Analysis of ZnS and MgF2 layered nanostructures grown by glancing angle deposition for optical design

This study investigated the multilayer growth and properties of ZnS and MgF₂ using glancing angle deposition. We used deposition angles of 85°-89° for ZnS and 70°-88° for MgF₂ to obtain the structural properties. The film properties primarily followed Tait's rule with a deposition angle of less than 87° in the vapor flux. However, film growth with a vapor flux angle of 88°-89° followed the tangent rule. Mathematical and cross-sectional scanning electron microscopy examinations found a transition point for the growth mechanisms at 87°, which comes from an extreme angle property for glancing angle deposition. We also performed mathematical derivations for the well-known empirical formula of the tangent rule and its generalized version. To stabilize the interface structure and surface roughness of multilayer structures, film growth at slightly tilted angles is recommended. Based on these results, an optical structure was designed, fabricated, and analyzed for a 550 nm wavelength pass filter on a glass substrate.

Effect of Pt and Au current collector in LiMn2O4 thin film for micro-batteries

The crystal orientation and morphology of sputtered LiMn₂O₄ thin films is strongly affected by the current collector. By substituting Pt with Au, it is possible to observe in the x-ray diffraction pattern of LiMn₂O₄ a change in the preferential orientation of the grains from (111) to (400). In addition, LiMn₂O₄ thin films deposited on Au show a higher porosity than films deposited on Pt. These structural differences cause an improvement in the electrochemical performances of the thin films deposited on Au, with up to 50% more specific charge. Aqueous cells using thin film based on LiMn₂O₄ sputtered on Au or Pt as the cathode electrode present a similar retention of specific charge, delivering 85% and 100%, respectively, of the initial values after 100 cycles. The critical role of the nature of the substrate used in the morphology and electrochemical behaviour observed could permit the exploration of similar effects for other lithium intercalation electrodes.

Structural control in porous/compact multilayer systems grown by magnetron sputtering

In this work we analyze a phenomenon that takes place when growing magnetron sputtered porous/compact multilayer systems by alternating the oblique angle and the classical configuration geometries. We show that the compact layers develop numerous fissures rooted in the porous structures of the film below, in a phenomenon that amplifies when increasing the number of stacked layers. We demonstrate that these fissures emerge during growth due to the high roughness of the porous layers and the coarsening of a discontinuous interfacial region. To minimize this phenomenon, we have grown thin interlayers between porous and compact films under the impingement of energetic plasma ions, responsible for smoothing out the interfaces and inhibiting the formation of structural fissures. This method has been tested in practical situations for compact TiO₂/porous SiO₂ multilayer systems, although it can be extrapolated to other materials and conditions.

High Specific Power Dual-Metal-Ion Rechargeable Microbatteries Based on LiMn2O4 and Zinc for Miniaturized Applications

Miniaturized rechargeable batteries with high specific power are required for substitution of the large sized primary batteries currently prevalent in integrated systems since important implications in dimensions and power are expected in future miniaturized applications. Commercially available secondary microbatteries are based on lithium metal which suffers from several well-known safety and manufacturing issues and low specific power when compared to (super) capacitors. A high specific power and novel dual-metal-ion microbattery based on LiMn₂O₄, zinc, and an aqueous electrolyte is presented in this work. Specific power densities similar to the ones exhibited by typical electrochemical supercapacitors (3400 W kg^-1) while maintaining specific energies in the range of typical Li-ion batteries are measured (∼100 Wh kg^-1). Excellent stability with very limited degradation (99.94% capacity retention per cycle) after 300 cycles is also presented. All of these features, together with the intrinsically safe nature of the technology, allow anticipation of this alternative micro power source to have high impact, particularly in the high demand field of newly miniaturized applications.