Analytical Solutions Along the Lithium-Ion-Battery Lifecycle
Thu 8 Jun, 2023
Quality as the main driver
To keep global warming in check, we need a worldwide mindset shift – especially in the field of energy supply. This can only be achieved if the industry takes a step out of the comfort zone of relying on ever-available fossil fuels and towards variable but sustainable forms of energy.
With new ways of thinking and smart adaptive technologies, our highly technologized daily lives can be sustained in a climate-friendly way. Electromobility is growing and there is an ever-increasing international focus on energy storage, not least because of the growing awareness of climate change and the increasing sanctions on CO2 emissions.
Lithium-ion batteries play a crucial role in this. For these to actually be sustainable and efficient as an alternative form of energy requires pioneering spirit. Analytik Jena's highly accurate analytical measurement techniques play a key role here – from exploration, development and production to quality control, recycling and controlling possible emissions into the environment.
Fundamentals – the function of a lithium-ion battery
Although lithium-ion batteries are relatively simple in structure, they involve many factors that require clarification. The combination of different materials - from solid to liquid, inorganic and organic – increases the complexity.
The battery cell of a lithium-ion battery consists of two electrodes: a negative graphite electrode (anode) and a positive lithium metal oxide electrode (cathode). There is also a thin electron-insulating layer (separator) impregnated with the electrolyte (liquid organic medium that conducts ions). During charging, the lithium ions in the electrolyte migrate through the separator from the cathode to the anode, allowing the latter to accept additional electrons. During the process of discharging, the electrons travel in the opposite direction through the external circuit back to the cathode. This converts chemically stored energy into electrical energy and releases it.
Demands on the promising new form of energy
The value chain of Li-ion batteries consists of six main stages that form a closed loop, from raw material extraction to battery cell recycling:
- Mining of raw materials
- Lithium-ion battery production
- Battery cell production
- Battery use
At every stage of the lithium-ion battery value chain from extracting and processing the valuable raw materials to quality assurance in production and material recovery during recycling, it is important to know which elements are present and the quantities of these to ensure the highest quality and safety.
Mining companies must therefore quantify the most important elements even before mineral extraction. It is also necessary for battery manufacturers to monitor impurities in raw materials to ensure product quality. Furthermore, it is necessary to control environmental emissions and comply with the prescribed limits for heavy metals. Recycling companies are also required to check the purity of recovered materials and comply with environmental regulations.
But how can these requirements be met? Currently, both the mining of raw materials and the production of lithium-ion batteries largely takes place in China, and the European market has been using these imports. A lithium discovery in the Osterzgebirge (Eastern Ore Mountains) in Saxony could make Germany more independent in lithium battery production in the future, as it is estimated that around 125,000 metric tons of lithium are stored under the ridge of this mountain range.
In addition to possible mining areas, the production of lithium-ion batteries has also been on the rise in Germany since 2021. Gigafactories for e-batteries are to be built in several German regions by 2024. However, empirical values, let alone standardized procedures and norms, are few and far between, especially in production and recycling.
Companies such as Analytik Jena are therefore currently working together with industry to develop valuable knowledge based on scientific findings and the most suitable methods. The goal is to develop high-quality and ecologically and economically valuable products and to establish meaningful standards. Reliable, sensitive and high-performance analytics is the linchpin in this process.
In the following, we first consider the upstream process, i.e. the exploration of raw materials and their refinement, for which requirements and best practices have already been established in some cases.
Upstream: Mining and refining
80 percent of the total value of a Li-ion battery cell is determined by the raw materials used. It is therefore important to focus on the highest level of quality as early as the ore extraction stage.
In addition to access to the appropriate mines, another key factor for high-quality raw materials is an understanding of the relevant processes for extracting raw materials from the mine ores.
1. Mining the raw materials
The following raw materials are typically required to manufacture lithium-ion batteries:
- Lithium carbonate (Li2CO3) forms the main component of the battery (cathode). To meet the increasing demand for lithium, more lithium must be extracted from existing or new sources. These include seawater brines and lithium-bearing underground brines and geothermal sources. Brines are underground reservoirs that contain high concentrations of dissolved salts, which in turn may contain lithium in economically significant concentrations and quantities. Salar brines are those that occur beneath dried-up lakes and are important sources of lithium. Mining sites with the largest market shares include those in Australia, Chile and the USA.
- Graphite is mostly used to make the anode and is largely sourced from China.
- Cobalt is mainly extracted in mines in the Democratic Republic of the Congo, but also in Australia.
- Nickel is largely mined in mines in Brazil, Canada, Russia and Australia.
- Miscellaneous metals such as aluminum, copper, and manganese.
The most important resource for lithium-ion batteries, lithium or lithium metal oxides LiMO2 (i.e. LiNixMnyCozO2), is very common, but its extraction is extremely costly and requires a combination of chemical processes and separation processes that are very energy intensive.
Graphite is also widely available, and its extraction is relatively easy. It can be obtained both by mining and via chemical processes (the conversion of other carbon compounds).
Cobalt, on the other hand, is a very rare commodity and is found almost exclusively in the Democratic Republic of Congo. The extraction of cobalt requires a combination of mining and chemical processes, both of which demand a great deal of energy.
Nickel is a widely used commodity and is found in many countries. Like graphite, nickel can be extracted by both mining and chemical processes.
Challenges and solutions
To produce high-performance cells for long-lasting lithium-ion batteries, manufacturers rely on raw materials with the highest degree of purity. Even before extracting lithium and other raw materials required for lithium-ion battery production, suppliers must determine their content in the brine so that they can control the extraction process and the quality of the final product.
The exploration and recovery of lithium and lithium compounds therefore requires powerful analytical technologies. ICP-based analytical techniques ICP-OES (inductively coupled plasma optical emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry) are routinely used for this purpose, as well as the less expensive AAS (atomic absorption spectrometry) techniques. However, despite their good suitability, these techniques often reach their limits due to the high total dissolved solids (TDS), the high density of the solutions, and the possible accumulation of algae and undissolved particles in the brine. Any undissociated matrix in samples with a high TDS content can deposit in the sample introduction system or lead to extinction of the plasma, thus affecting the long-term stability of the measurements. Accordingly, the salt matrix represents a critical factor in the analysis.
In addition to brines, certain rock types, such as pegmatites, also contain minerals that contain lithium. These include minerals such as spodumene, lepidolite and petalite. However, compared to other felsic rock types such as granites, many pegmatites are not particularly enriched in lithium. Microcline, wolframite, and pollucite are also recovered from certain pegmatites and the coarse-grained, complex zoned structure of pegmatites can be challenging when trying to collect sufficiently representative samples.
Both melt and acid digestions are effective for almost all lithium minerals and the resulting solutions can be determined by ICP-OES, ICP-MS, and AAS, depending on the expected grade and element series of interest. If other elements such as tin, tantalum, and niobium are required, fusion digestion is recommended to ensure the complete dissolution of refractory minerals containing these elements. The analysis of such samples is challenging for ICP-based analytical techniques for several reasons: The sample solutions usually have a high content of total dissolved solids (TDS) and a high density. In saline solutions, the presence of undissolved particles is also likely. The sample matrix may also deposit itself in the sample delivery system or attenuate the plasma, which will have a long-term effect on the stability of the measurements. Ore or brine samples often contain unknown amounts of various elements. This unknown composition can lead to spectral and physical perturbations that can affect the accuracy of the measurements. Accordingly, a robust measuring instrument and methodologically correct sample preparation are critical.
Comprehensive elemental analysis of samples with high matrix content using ICP-OES
Routine elemental analysis of large numbers of matrix-rich samples requires robust analytical technology with stable plasma. The ICP-OES PlasmaQuant 9100 is ideally suited to meet the high demands of this challenging analysis in the field of lithium-ion batteries. The perfect interplay of spectral resolution, matrix tolerance and sensitivity opens up enormous analytical potential for trace element analysis in almost any sample type, especially for samples with a high matrix content. Thanks to its high-frequency generator, which produces an exceptionally robust plasma, it can measure any sample type with minimal effort and maximum emission yield.
Quantitative determination of metal impurities in Li-ion battery raw materials using ICP-MS
ICP-MS technology offers further testing possibilities for the quality control of raw materials. It can be used to analyze raw minerals, extraction and refinery products for major elements and impurities at high throughput. Compared to atomic absorption spectrometry and ICP-OES, ICP-MS is faster, more accurate and more sensitive.
Although the purity of most Li salt compounds is currently still determined using ICP-OES, it can only measure a few elements due to its sensitivity limitations. In the coming years, the requirements for higher purity of raw materials for longer battery life will continue to increase.
Manufacturers of high-quality batteries will then have to ensure purity of 99.95-99.99 percent. This is likely to lead to an increase in the number of elements that need to be analyzed and thus the relevance of ICP-MS in the analysis of Li-ion battery raw materials. In the future, the analysis of impurities could be switched from ICP-OES to the more powerful ICP-MS.
Cost-effective elemental analysis using AAS as an alternative technique
Atomic absorption spectrometry (AAS) is a widely used, robust and cost-effective analytical technique with broad application, including for quality assurance in lithium battery manufacturing. By providing detailed analysis of the exact elemental compositions in battery components, AAS measurement technology can provide production with valuable information to ensure consistent production quality. Slight deviations from the "design specs" provide indications of impurities and thus reduce battery performance and lifetime.
Flame AAS is a relatively simple and inexpensive method and is suitable, for example, for the analysis of metal ions such as lithium, cobalt, nickel and manganese in the electrolyte solution of lithium batteries. Graphite furnace AAS is a more sensitive and precise method, which can be used for example, for the analysis of trace elements in the cathode materials of lithium batteries. The contrAA 800 with its unique HR-CS (High-Resolution Continuum Source) technology offers special advantages in terms of detection strength and measuring speed. With the fast-sequential flame operation of the contrAA 800, the measurement time can be reduced by up to 30 percent compared to conventional AAS. The graphite furnace technology of the contrAA 800 has an additional application and is therefore particularly relevant for the determination of fluorine content.
Overall, the application of AAS in lithium battery technology plays an essential role in ensuring the quality and safety of these critical energy sources.
Robust analysis of TOC impurities in raw materials used in cathode manufacturing
For cathode fabrication, active material, which serves to intercalate the lithium ions, is deposited on aluminum foil. To date, the following cathode materials are established on the market: NMC (lithium nickel manganese cobalt oxides), NCA (lithium nickel cobalt aluminum oxide), LFP (lithium iron phosphate) and LMO (lithium manganese oxide). The active materials are usually produced from a multi-stage process whose starting materials are usually salts of the characteristic metals.
For example, nickel sulfate, manganese sulfate, cobalt sulfate and lithium carbonate (or lithium hydroxide) are used for NMC production. These salts must be "battery grade," i.e., they must have a certain purity. The lower the degree of impurity of the raw materials, the lower the risk that electrochemically inert phases can form that impede the transport of the Li-ions, reducing the reversible capacity and thus the battery performance.
For this reason, these salts are often offered on the market as "battery grade" quality. In addition to metal impurities, it is also important to analyze organic impurities, which can be determined using the sum parameter TOC (Total Organic Carbon). For this purpose, the salt is placed in an aqueous solution and then analyzed with a TOC analyzer for aqueous samples. The method of choice for TOC determination is high-temperature digestion followed by NDIR detection of the carbon dioxide formed from the organic compounds.
The highly saline matrix poses a particular challenge here – it leads to greater wear of the combustion tube and the catalyst contained therein due to the deposition of metal oxides and salts. The multi N/C 3100 with its high detection strength and robust detection technology provides a reliable solution with its optimized combustion tube fillings as well as method and parameter settings, which help to minimize these effects and thus significantly reduce maintenance cycles and expenses.
ICP-OES and ICP-MS analysis of elemental impurities in anode and cathode material as well as in the electrolyte
In addition to the sum parameter TOC, the contamination of the cathode material by (metallic) elements is also highly relevant to the performance of lithium-ion batteries, as mentioned above. Current standards recommend ICP-OES to measure this content as manufacturers are currently required to keep the most important contaminants, such as chromium, iron, copper, zinc and lead, at a concentration below 1 mg/kg (ppm).
However, as battery technologies advance, the level of contamination is becoming lower and lower, making it difficult to measure accurately with ICP-OES.
As a result, manufacturers are exploring ICP-MS as a method that offers even greater accuracy. Analytik Jena's PlasmaQuant MS has the most sensitive detection limits for the relevant elements as well as a robust and efficient plasma. Analytik Jena's ICP-MS systems also feature excellent resilience to interference, thanks to the user-friendly integrated collision reaction cell (iCRC).
The quality and purity of the anode material also has a decisive influence on the capacity of the anode and thus on the performance of the Li-ion battery. In recent decades, graphite has established itself as the preferred starting material for the lithium battery anode. This is due in part to its excellent material properties, availability and relatively low cost. Most of the graphite used in the manufacture of lithium-ion batteries is produced and refined in China. The technique typically used to analyze impurities is ICP-OES. Corresponding European standards are required for the Chinese limits currently applied to the elements of sodium, aluminum, iron, cobalt, chromium, copper, nickel, zinc, molybdenum and sulfur. ICP-MS is used as the analytical technique for the heavy metals cesium, mercury, lead and chromium.
The increasing performance of Li-ion batteries is accompanied by increased demands on the anode material. Many battery manufacturers are therefore interested in measuring a wider range of elements, in some cases below the detection limits achievable with ICP-OES. Similarly to the cathode material, ICP-MS is being tested as a promising alternative to ICP-OES.
In addition to the cathode and anode materials, the electrolyte is the third factor influencing the performance of Li-ion batteries. The performance of the electrolyte, in turn, is strongly determined by possible elemental impurities. In this context, ICP-OES is also the most commonly used technique to determine impurities in electrolyte salts or other starting materials. For laboratories that want to determine trace elements in the sub-µg/kg (ppb) range, however, ICP-OES is not sufficient. Here, ICP-MS is more suitable due to its speed, low detection limits and wide-ranging element coverage.
3. Wastewater monitoring
The entire manufacturing process of a lithium-ion battery can cause significant water pollution and contamination of wastewater. The production process involves the use of various chemicals such as solvents, acids, and alkalis that can contaminate the process water if not properly handled and disposed of. Water used in the production process can be contaminated with heavy metals such as nickel, cobalt, and manganese, which must be accurately and reliably quantified. Wastewater from lithium battery production can also contain organic solvents that can be toxic to aquatic life and persistent in the environment. Consequently, wastewater treatment throughout the lithium lifecycle presents complex analytical challenges. A major challenge is controlling environmental emissions of heavy metals and organic solvents in wastewater and complying with regulatory limits.
Atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) as well as TOC/TNb sum parameter analysis are all accurate and reliable techniques for this purpose, depending on the element concentration.
Instruments for multi-element analysis, such as Analytik Jena's contrAA, are particularly suitable for wastewater analysis of high and medium concentrations. The high-resolution atomic absorption spectrometer with continuum emitter makes it possible to process many samples with different matrices and a variety of analytes. It is also robust, easy to operate and can be fully automated for daily routine operation with the autosampler AS-FD and its automatic dilution function.
An ideal choice for measuring the smallest element concentrations are the ICP-OES instruments often referred to in relevant industry standards, such as the PlasmaQuant 9100 Elite. The combination of multiple analytical techniques and careful sample preparation are crucial for overcoming the analytical challenges in the wastewater treatment of lithium battery production.
Occasionally, trace elements must also be measured in a standardized way according to ICP-MS; a corresponding European standard is already being prepared. Since the manufacturers are subject to a self-declaration obligation, the elemental techniques and sum parameter analysis are also obligatory in the process monitoring of wastewater treatment.
Wastewater contamination by organic solvents, especially those with compounds that contain nitrogen (TNb - Total bound Nitrogen) can be optimally analyzed using TOC/TNb sum parameters. The catalytic high-temperature TOC/TN analyzers of the multi N/C series with their flexible automation solutions, robust and reliable sample feeding, oxidation and detection offer tailor-made solutions for this purpose.
Continuous monitoring and regular analysis of wastewater samples make it possible to identify potential environmental impacts and take appropriate measures to minimize environmental pollution.
Ready for the energy shift
Lithium production grew by 335 percent from 2008 to 2018 – and the upwards trend continues. Up to 14 million metric tons of lithium are estimated to remain in reserve for processing.
To process this into batteries with the highest purity and thus longevity, while also protecting the environment from the by-products of production, requires reliable, powerful and precise techniques and equipment.
Analytik Jena has a broad product portfolio in all the relevant analytical methods presented above. Our global presence and expertise, also in the field of spectroscopic analysis of complex ores and solutions, make us an ideal partner around the life cycle of lithium-ion batteries.
Our instruments in the field of ICP-OES, ICP-MS, AAS and TOC/TNb enable the complete mineralogical and chemical characterization of lithium-bearing ores, concentrates and brine solutions and also ensure the required environmental analysis. Discover our portfolio and applicable solutions for your specific challenge or contact us.
Source: United States Geological Survey – USGS
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Analysis of Cathode Material of Lithium-Ion Batteries Using HR-ICP-OES (DE)
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