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

Physical vapor deposition technology for coated cutting tools: A review

A hybrid PEMFC/supercapacitor device with high energy and power densities based on reduced graphene oxide/Nafion/Pt electrode

Growth mode during initial stage of chemical vapor deposition

This paper demonstrates that sputtered Ti-Cu is a superior barrier and seed layer on glass and organic panel substrates, over traditional electroless seeding, for the fabrication of ultra-fine copper traces (2–5µm) on dry film polymer dielectrics for high-density 2.5D interposers. The current semi-additive processes using electroless Cu seed face several challenges in scaling the copper trace widths below 5µm due to two main reasons: high-roughness of dielectric and high-thickness of copper seed. In this paper, both the above limitations are addressed by an advanced Physical Vapor Deposition (PVD) process that can be scaled to large panels with high throughputs. The PVD process developed in this study is capable of depositing Ti-Cu barrier and seed layer on 500 mm size panels at a low enough temperature for dry film polymer dielectrics of glass transition temperatures (T g ) of 150–160°C. The superiority of sputtered Ti-Cu over the conventional electroless Cu seeding for achieving good and reliable adhesion between Cu and dry film polymer dielectrics was investigated by peel strength measurements after highly-accelerated stress tests (HAST). The results indicate that sputtered process results in higher peel strengths and without adhesive failures at the Ti-Cu-polymer interfaces. Adhesive failures, however, were observed with the traditional electroless seed processes. In addition, the PVD processes resulted in small 2–5µm Cu traces on smooth dielectric films like ZS-100, requiring no desmear treatment. Such a process promises to be scalable to large panels leading to low-cost fabrication of high-density 2.5D interposers.

Although batteries have been successfully employed in light-duty vehicles (hybrid and fully electric cars), batteries still find it is hard to satisfy power-hungry platforms such as trucks, trams, and buses. Conventional lithium ion batteries (LIB) could provide power density less than 3 kW/kg with relatively moderate energy density. On the other side, supercapacitors (SCs) that are known to provide power density of more than 10 kW/kg have a very low energy density of less than 1 Wh/kg and thus, SCs could not be used solely as energy storage. However, employing anode from LIB and electrode from SC together in a single system would benefit both high energy and power density, which system is-so called lithium ion capacitor (LIC). To date, so many attempts have been done to investigate the best anode material combination with activated carbon (AC) to obtain high performance LIC. The anode materials that are commonly utilized in LIB such as graphite, hard carbon, Li4Ti5O12 (LTO), Fe3O4, SnO2, and silicon based material have been extensively studied for LIC. Graphite that is known as an ubiquitous anode material in LIBs provided relatively high energy density of c.a. 100 Wh/kg and maximum power density of less than 2 kW/kg in LIC. Among all, LTO application was found to be the least desirable material for LIC since it provided relatively low maximum energy and power density, which was merely less than 40 Wh/kg and 2 kW/kg, respectively, due to its low conductivity and high voltage plateau at around 1.5 V. Grphene has been used to reinforce rate capability of Fe3O4 and it demonstrated promising energy density as high as 86 Wh/kg. However, the maximum power density of the enhaced electrode material was only 2.6 kW/kg. Higher power LIC can be achieved by harnessing hard carbon anode material, which displayed maximum power density of about 50 kW/kg. However, the high power density of hard caron in LIC was compensated by extremely low energy density of less than 2 Wh/kg. Herein, we investigate the electrochemical performance of LIC by using silicon oxycarbide (SiOC) as the anode and the AC from biomass (Zalacca salacca) peels as the cathode to provide massive power while maintaining the energy density relatively high. SiOC showed an outstanding rate capability performance indicated by relatively high discharge capacity of over than 200 mAh/g at current density of 80 A/g. The excelent rate capability was attributed to the fast lithium diffusion in SiOC, which was represented by high lithium diffusion coefficient (DLi+) of 5.1 × 10-6 cm2/s. Meanwhile, the AC derived from biomass is promising since its surface area (c.a. 2600 m2/g) and capacitance (163.7 F/g) was significantly higher than that of commercial AC. Combination of SiOC and AC derived from Zalacca salacca in a single unit of LIC could be used to provide a massive power density of 155kW/kg while maintained relatively high energy density of 25 Wh/kg. Moreover, the resulting LIC demonstrated highly stable cycle retention at high C-rate. After reaching equilbrium state, the cycle retention of LIC at 50C was 99.4% after more than 40,000 cycles. At higher C-rate of 100C, the cycle retention of the LIC was 99% even after more than 75,000 cycles. The present study indicates that LIC design based on SiOC and AC from Zalacca salacca peels is suitable for energy storage in high-duty platforms such as trucks, trams, and buses.

Functionalized interfacial cover design toward pure silicon anode for high power density lithium–ion capacitor

The ability to engineer electrode microstructures to increase power and energy densities is critical to the development of high-energy density lithium-ion batteries. Because high tortuosities in porous electrodes are linked to lower delivered energy and power densities, in this paper, we experimentally and computationally study tortuosity and consider possible approaches to decrease it. We investigate the effect of electrode processing on the tortuosity of in-house fabricated porous electrodes, using three-dimensionally reconstructed microstructures obtained by synchrotron x-ray tomography. Computer-generated electrodes are used to understand the experimental findings and assess the impact of particle size distribution and particle packing on tortuosity and reactive area density. We highlight the limitations and tradeoffs of reducing tortuosity and develop a practical set of guidelines for active material manufacture and electrode preparation.

Strontium phosphide-polyaniline composites for high performance supercapattery devices

Developing dielectric capacitors with both a high power density and a high energy density for application in power electronics has been a long-standing challenge. Glass-ceramics offer the potential of retaining the high relative permittivity of ceramics and at the same time of exhibiting the high dielectric breakdown strength and fast charge/discharge rate of glasses, thus producing concurrently high power and energy densities in a single material. In this work, glass-ceramics are fabricated to achieve simultaneously high power and energy densities, high efficiency, and thermal stability by tuning the glass crystallization process via a suitable nucleating agent and a high oxygen partial pressure. Under the same practical charge-discharge test conditions, the as-prepared glass-ceramics combine the high energy density of ceramics and ultrafast discharge rate of glasses, producing the highest power density among glass- and ceramic-based dielectric materials. This work demonstrates the significant potential of achieving both high power and energy densities in glass-ceramics by optimizing the glass crystallization process.

O 2 diffusion through Aluminium-Copper (Al-Cu) layer deposited by physical vapor deposition (PVD) process can be investigated using TEM (Transmission Electron Microscope) coupled with EDX (Energy Dispersive X-ray) line scan. During PVD process, the wafer is hot after Al-Cu deposition thus a cooling step is required before the wafer is unloaded (vacuum release). Higher amount of O 2 diffusion was observed for sample with 30s cooling time compared to the one with longer cooling time which is 60s. This indicated that higher wafer temperature induce higher O 2 diffusion rate in Al-Cu when exposed to air. No O 2 diffusion within tungsten (W) layer was observed. Al-Cu exposure time to air before it is coated with photoresist is also studied. Wafer with 60s cooling time and 16 hours exposure time in air has O 2 diffusion level is higher than the wafer with same cooling time but with 8 hours exposure time. The TEM-EDX line scan profile indicated that at room temperature, the O 2 continue to diffuse through Al-Cu layer at lower rate until its surface is coated with photoresist. The O 2 diffusion as analyzed by TEM-EDX method is a function of temperature and time. The higher the temperature, the faster the O 2 diffusion while the longer the exposure time to air, the more the diffusion of O 2 into Al-Cu.

Li-ion batteries are commonly used in portable electronic devices due to their outstanding energy and power density. However, in order to reach the requirements of the automotive industry for next-generation electric vehicles regarding safety, life-time, energy density, and fast charging further developments are inevitable. Additionally, a reduction of material and production costs is needed to improve the price competitiveness. In this contribution we will present a study of different electrode design concepts with the goal to optimize energy and power density of Li-Ion battery electrodes and cells by microstructure resolved electrochemical simulations [1]. State-of-the-art NMC positive electrodes with different thickness and density were prepared and characterized electrochemically in collaboration with our partners [2]. In a next step reconstructions of the electrodes were created with the help of synchrotron tomography and a 3D stochastic microstructure generator [3], [4]. The resulting microstructures are then input to electrochemical simulations within our software BEST and good qualitative agreement between the simulations and experimental data can be reported. Especially, the pivotal role of inactive materials for battery performance could be demonstrated through microstructure-resolved impedance simulations. Based on these results different design concepts were evaluated regarding their energy and power density. An attractive strategy to decrease the share of inactive materials is to increase the mass loading of the electrodes [5], [6]. This concept provides a high theoretical capacity and energy density. However, it also shifts the transport limitations of shuttling lithium ions in the electrolyte to lower C-rates and reduces the rate capability and practical capacity of the cell [6], [7]. In order to enable a fast charging of the batteries structuring techniques are investigated. A promising concept is the laser perforation of the electrodes which creates a hierarchical pore network with macroscopic transport pathways between anode and cathode. Our simulations confirm the beneficial effects which are found in the experiments and we perform an extensive simulation study in order to investigate the effect of different hole geometries and configurations on battery performance and life time. Our study shows that this simulation-based approach is a powerful and efficient tool for the analysis and design of porous electrodes for Li-ion batteries. Acknowledgement This work has been funded by the ‘Bundesministerium für Bildung und Forschung’ within the project HighEnergy under the reference numbers 03XP0073D.

ConspectusLithium-ion batteries (LIBs) are nearly ubiquitous energy storage solutions, powering devices ranging from consumer electronics to electric vehicles. To advance these applications, current LIB research efforts are directed toward improving energy and power densities, cyclic lifetimes, charging speeds, and safety. These parameters are intrinsically tied to properties of the active electrode materials, such as the redox mechanism, chemical composition, and crystal structure. One particularly challenging issue is that the active electrode materials that possess higher theoretical energy densities are generally more susceptible to degradation during cycling. A notable example is the family of layered multicomponent transition metal oxides, which is the incumbent class of active LIB cathode materials for electric vehicles. To increase their theoretical capacities, the transition metal fraction in these materials is trending toward higher Ni content. However, Ni-rich chemistries suffer from electrochemical, crystallographic, and mechanical degradation that increase in severity with increasing Ni content. Furthermore, alternative high-energy cathode materials, including overlithiated layered oxides and disordered rock salt materials, present additional stability challenges that must be overcome before they can be realistically incorporated into LIB technology.The chemomechanical degradation in high-energy LIB cathode materials occurs at multiple length scales. Point defects, such as antisite defects or vacancies, are commonly generated during electrochemical cycling and can contribute to the loss of cyclable active material. At both the primary and secondary particle level, electrochemical cycling also induces significant volumetric changes and state-of-charge heterogeneity, generating regions of high stress and strain that are precursors to mechanical fracture. Finally, at the electrode level, nonuniform charge transfer reactions throughout the electrode can lead to locally overcharged regions that become sites of enhanced degradation. To address these issues, active cathode material design and electrode engineering are being heavily pursued to accelerate improvements in LIB energy density. To consolidate the current understanding of chemomechanical degradation and provide guidance on mitigation strategies, a comprehensive overview of degradation mechanisms across multiple length scales is critically needed.In this Account, we first outline the origins of chemomechanical degradation for high-energy LIB cathodes, including layered oxides, overlithiated layered oxides, and disordered rock salt structures. Specifically, we delineate the thermodynamic and kinetic origins of defect generation at the atomic level and then progress to the kinetic origins of broader degradation mechanisms at the particle level and electrode level. Next, we discuss strategies for minimizing chemomechanical degradation in high-energy LIB cathodes at multiple length scales. Finally, we provide a forward-looking perspective on how to accelerate progress toward practical high-energy LIB cathodes, including emerging methods to map state-of-charge heterogeneity, efficient data processing techniques, and improved strategies for spatially identifying chemomechanical degradation. We also propose engineering solutions for mitigating chemomechanical degradation, such as grain boundary engineering, modifying the active material particle morphology, and electrode architecture design. Since many of these suggestions can be applied irrespective of cathode chemistry, this Account is likely to be broadly applicable to the diverse set of ongoing efforts to realize high-energy LIBs.

Modelling, Simulation and Control of Roll-to-Roll Physical Vapor Deposition Processes

Our increasing energy demands have spurred a rigorous search for renewable energy sources to reduce our dependence on fossil fuels. However, efficient use of renewable energy is possible only with advances in both energy generation and storage. Today’s batteries and capacitors, which are the main energy storage devices, cannot meet the world’s demand for combined power and energy densities. To enhance the viability of such energy storing devices, the Clemson Nanomaterials Center (CNC) has developed a mix of scalable processes for carbon nanotube-based hybrid electrodes that show promise as a cost-effective alternative to standard activated carbon-based electrodes. Working together with industrial partners, CNC has fabricated supercapacitors with energy and power densities in the range of ~11–35 Wh/kg and ~1.2–9 W/kg, respectively. Although this research development is transformative, further studies to optimize the separator and electrolyte technologies are needed to maximize both the energy and power density in a single device.

Lithium-Ion Batteries receive growing attention because of their potentially high energy and power density, which are important requirements for automobile applications. Reports agreed that the positive electrode is hereby the performance limiting cell component. NxMyCz (nickel manganese cobalt spinel) is one of the most promising cathode materials, both due to its rather high operating voltage and to either high power or energy density [1]. Hereby, a compromise between high power (thin layers and, i.e., high porosity) and high energy density (thick layers and, i.e., low porosity) has to be reached, in particular for automotive applications. This demands for an extended understanding of the interplay between microstructure parameters and chemical stoichiometry of NMC cathodes on cell performance characteristics. In this study, two NMC - cathodes recovered from commercial high energy and high power cells are analyzed (i) by SEM and X-ray tomography and (ii) by Electrochemical Impedance spectroscopy (EIS). By evaluating the impedance spectra measured at 0 to 40°C and at SOC 0 to SOC 100 by the distribution function of relaxation times (DRT) [2], a physically motivated transition line model [3] was established. The microstructure parameters required for a quantitative analysis of the electrochemical loss processes were obtained by X-ray tomography data. Additionally, the exact composition is determined by energy dispersive X-ray spectroscopy (EDX) investigations The results confirm, that a NMC electrode custom tailored for high energy density is rather thick (70 µm) and made of large low-porous agglomerates of primary particles, as described in [4]. The significant difference between the NMC cathode of a high energy and a high power cell however is not, as expected, a significantly higher porosity, but a sophisticated combination of small carbon black particles and elongated carbon black fibers, enabling high discharge currents. The tortuosity of the electrode pores, which represent the transport pathways for the liquid electrolyte, is low for the high power cell, which raises the effective electrolyte conductivity significantly, when compared to the high energy cell [4]. Furthermore the high power cell features a special compound of two different NxMyCz active materials. By including all the results from EIS, DRT, X-ray tomography and EDX, an evaluation of the influence of composition and microstructure on performance characteristics of the NxMyCz cathodes will be presented.