What is XPS?

X-ray photoelectron spectroscopy (XPS) is a powerful surface analysis technique used to identify the elements in and the chemical states of the top layers of materials. It works by bombarding the surface of a material with X-rays (photons) and then measuring the kinetic energy of the photoelectrons ejected from the surface of a material. This energy is directly related to the photoelectrons’ binding energy within the parent atom and is characteristic of the element and its chemical state. Only electrons generated near the surface can escape without losing too much energy for detection. As a result, XPS data is obtained only from the top few nanometers of the surface. XPS surface selectivity, combined with quantitative chemical state identification, makes XPS highly useful in many applications, including battery research.

Vital role of battery research

Batteries have a vital role to play in the world’s transition from fossil fuels to renewable energy. In 2022, EVs accounted for 10% of global vehicle sales and by 2030 they are expected to reach 30% of global vehicle sales.  Governments around the world are contributing to this growth through policies that are directing billions of dollars into battery research and manufacturing and by providing subsidies for consumers to purchase EVs.  Ambitious cost and performance targets for the electrification of transportation will require the development of next-generation batteries produced on a commercial that are cost-effective, safe, renewably sourced, and high-performing with long lifetimes.

How XPS is used in battery research

There are multiple components and interfaces that are crucial to understand to develop high-performing and stable batteries. These include the cathode, anode, separator, electrolyte, and all interfaces formed between these layers, particularly the electrode-electrolyte interfaces. XPS can be used to study all of these materials and interfaces, such as next-generation cathode/anode active materials and how their composition changes with cycling; how the solid electrolyte interphase (SEI) layer varies in composition as a function of depth; and how surface pre-treatments affect the chemistry of the active electrode material. The quantitative chemical-state information provided by XPS makes it a versatile tool to understand many properties and guide the design of optimized batteries that meet ambitious targets.

Battery research challenges and XPS solutions:

• Analyzing SEI layer growth: Ongoing charging and discharging of a battery causes the SEI layer to form on the anode, reducing battery capacity. Analysis of the SEI layer helps researchers better understand and control this phenomenon and thereby improve battery performance and longevity. XPS depth profiling can chemically characterize the complex mixture that makes up the SEI layer, from the anode side all the way to the electrolyte side, for chemical understanding of the entire layer.
• Investigating the role of impurities and contaminants: Impurities and contaminants in battery materials can adversely affect performance and safety. XPS is highly sensitive to trace elements and can identify the presence and identity ofimpurities or contaminants on the surfaces of battery materials, helping researchers understand the sources of impurities and their impact on battery performance.
• Understanding the stoichiometry of solid electrolyte films: Chemical state analysis provided by XPS can be used to identify the stoichiometry of materials, including depth profiling to quantify elements at each depth and track any differences in stoichiometry throughout a film.
• Studying interface chemistry: Interfaces between different components of a battery play a crucial role in battery performance and long-term stability. XPS provides insights into the chemistry of interfaces, helping researchers optimize interface design for enhanced performance.
• Examining degradation in separator chemistry: XPS can provide valuable insights into degradation in separator chemistry during a cell’s lifetime by analyzing the surface chemistry and composition of the separator material.
• Environmental impact and recycling: XPS can be used to analyze the chemical composition of battery materials before and after recycling processes. It can help assess the effectiveness of recycling methods and the feasibility of reusing materials.
• Analyzing in situ electrode cycling: In situ XPS experiments can provide real-time insights into the electrochemical behavior and surface chemistry of electrode materials during cycling.

The best XPS for battery research from SRC

PHI’s XPS instruments use a unique scanned, finely-focused X-ray beam to create X-ray induced secondary electron images (SXIs), similar to an SEM, for easy sample navigation with 100% certainty in analysis position.  This imaging capability can be used to easily drive around the sample in live mode or to save positions for compositional analysis including point or large-area spectroscopy, line scans, depth profiling, or chemical mapping. The size of the X-ray beam can be selected to support the efficient analysis of larger samples with homogeneous composition or small heterogeneities. This feature is indispensable for analyzing battery materials and interfaces, ensuring identification of impurities or other heterogeneities in composition, and absolute certainty that data is acquired from the exact feature of interest. In contrast to SEM/EDS, which has a typical analysis depth of 1-3 µm, XPS is a surface-sensitive technique with a typical analysis depth of less than 5 nm, making it better suited for the compositional analysis of ultra-thin layers and thin microscale sample features.

The PHI Genesis is the latest generation of PHI’s highly successful multi-technique XPS product line with PHI’s patented, monochromatic, micro-focused, scanning X-ray source. It is an easy-to-use, fully automated system with auto-tuning and calibration and multiple parking positions for high throughput. The fully integrated multi-technique platform of the PHI Genesis offers an array of optional excitation sources, sputter ion sources, and sample treatment and transfer capabilities that are all aligned to the same sample location. These features are essential in studying all relevant properties of advanced battery materials and interfaces, including small impurities or compositional heterogeneities, access to buried interfaces, electronic energy gap measurements, and operando experiments for a direct link between chemistry and performance. PHI Genesis offers high sensitivity and high throughput for large areas and small areas down to 5 µm and unique high-throughput non-destructive depth profiling using the optional hard X-ray Cr source. The instrument is fully customizable to address all analytical needs.

For more information on how PHI Genesis can be used to address your battery characterization challenges, please visit the PHI YouTube channel to watch a recent PHI.

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Click here to contact SRC and speak directly with experts on PHI’s Genesis.

The world of 3D Ceramic Printing has come a long way since the 1980s when it was considered suitable only for the production of functional or aesthetic prototypes, and a more appropriate term for it at the time was “rapid prototyping”. Today, the the precision, repeatability, and material range of 3D printing have increased to the point that some 3D printing processes are considered viable as an industrial-production technology, whereby the term “additive manufacturing” can be used synonymously with 3D printing.

Applications of 3D ceramic printing

In this article we are going to look at 3D printing—or additive manufacturing if you will—using ceramic materials for the following applications:

1) Production of ceramic foundry cores;

2) Optimization of optical instrumentation.

Types of ceramics used in 3D printing

Before we get too far into the weeds with the two applications highlighted above, let’s briefly have a look at the types of ceramics used in 3D printing. Generally speaking, the qualities of ceramic materials are: high strength, high dimensional stability (low coefficient of thermal expansion), low density, high resistance to abrasion and corrosion, and exceptional chemical stability. There is a variety of ceramic materials used in 3D printing, which are categorized into:

• Oxide ceramics: alumina, zirconia, silicore, alumina-toughened zirconia, cordierite, 8 mol% yttria-stabilized zirconia, silice SiO2, hydroxyapatite/TCP, and tricalcium phosphate;
• Non-oxide ceramics: silicon nitride and aluminum nitride.

3D Ceram Sinto, a leader in the world of 3D ceramic printing, offers a full range of ready-to-use ceramic pastes for use with their CERAMAKER printers. Naturally, they advise their customers on the critical issue of the ceramic paste best suited to the application at hand, but can also create ceramic paste formulations according to specifications provided by their customers.

3D Ceram ceramic paste

3D printing of ceramic foundry cores

Foundry cores are integral to the production of turbine blades for aviation, aero-derivative and land-based gas turbines. Up to now manufacturing cores has been a time- and labour intensive process. Today, in an effort to lower fuel consumption, improve turbine efficiency and decrease engine emissions, core designs are becoming increasingly complex. Making a complex, porous ceramic foundry core using conventional manufacturing processes involves making the core in several pieces and then assembling them manually. The likelihood of a problem occurring in this process is considerable, resulting in wasted time and materials—and excessively high costs.

Some of the constraints applied to core production:

• Dimensional accuracy +/- 0.1 mm
• Structural strength
• Surface roughness
• Material porosity

Additive manufacturing brings a new dimension to conventional industrial processes, allowing all of these elements to be controlled. In addition to saving time and materials and increasing productivity in the production of ceramic foundry cores, the technology delivers the following benefits:

• Design flexibility
• Possibility of more core complexity
• Quick creation of new designs
• Better responsiveness and productivity
• Increased profitability
• Maintenance of core strength

3D printing of optical instruments

3D printing is one of the key technologies for devising innovative solutions contributing to the optimization of optical instruments, such as a plane mirror for a front-end laser engine (galvo-mirror for high-energy laser application). 3D printing can greatly enhance the design and manufacturing of the optical substrate of such an instrument.

Two types of mirror

The use of additive manufacturing for the production of optical instruments has the following benefits:

• Parts are lighter because they feature more complex designs that incorporate holes and semi-closed structures
• Lead time is reduced as there is no need to manufacture and then lighten by machining a first draft
• Less ceramic is used, which reduces costs
• New, more complex and disruptive designs are possible
• New functions such as internal channels, electrical tracks and feedthroughs can be incorporated.

As a result of new additive manufacturing technology, optical substrates and mirrors can now be more compact, thus allowing for additional functions while still keeping volume and mass low.

Industrial 3D ceramic printers

We’ve touched on the ceramic pastes used in 3D ceramic printing and must do likewise with 3D ceramic printers. The number of ceramic 3D printers on the market has increased steadily in recent years and many industrial solutions are now available. Indeed, more manufacturers are offering professional solutions, capable of designing high-quality parts with increasing speed.

3DCeram Sinto is undoubtedly one of the historical players in ceramic additive manufacturing and has developed a professional range based on a stereolithography process. 3D Ceram Sinto’s CERAMAKER 3D printer family has the widest range and most

practical printing platforms of any company in the market, ranging from the C100 (100 x 100 x 150 mm) to the C3600 (300 x 300 x 100 mm). Taking shrinkage into account, you can produce parts with dimensions up to Ø500 mm  with the CERAMAKER C3600.