The demand for rechargeable lithium-ion batteries is growing fast and as a result, manufacturers have to meet challenging requirements for production quality and further battery development.
METTLER TOLEDO's extensive portfolio of analytical characterization solutions for the laboratory, and process analytical sensors and automated precision scales for manufacturing, support quality assurance (QA) development and quality control (QC) procedures of lithium-ion battery production.
Our innovative solutions support the various steps in the lithium-ion battery value chain – from the testing of raw materials and battery components, to production and final quality control.
The ever-increasing market for portable electronic devices, together with the increasing pace of the electric vehicle revolution, has resulted in an equally large demand for rechargeable batteries. Lithium-ion batteries (LIBs) are state-of-the art in this technology. This battery type exhibits high energy density as it is light yet powerful, good cycle durability as it can be charged and recharged without losing much energy each cycle, and a low self-discharge rate.
The lithium ion battery diagram illustrates the working principle of a lithium ion battery. LIBs store energy that is released by an electrochemical reaction between the anode and the cathode material. Both cathode and anode contain positively charged lithium ions.
During discharge, the oxidation reaction at the anode releases electrons and lithium cations. The electrons flow through an external wire to the cathode. To close the electric circuit, lithium cations flow through the liquid electrolyte and the separator to the cathode, where they recombine in a reduction reaction.
During charging, the reactions at the electrodes are reversed and the lithium ions flow in the opposite direction. The lithium ions do not partake in the overall electrochemical reaction and remain in their oxidation state.
The electrolytic solutions commonly used in commercial lithium ion batteries consist of organic solvents (mostly cyclic and linear carbonates), lithium salts and various additives. Electrolytes and other Li-ion battery materials must be free of water because even trace amounts react with the electrolyte to produce aggressive by-products including hydrofluoric acid that compromise battery performance and safety. As water has such a bad influence, the water content of the electrolyte needs to be tested as a matter of routine.
Coulometric Karl Fischer titration is the method of choice to determine the water content of electrolyte precisely and accurately. Not only water, but also the detrimental degradation product itself, hydrofluoric acid (HF), can be determined in the electrolyte. Acid-base titration has proven to be an accurate and reliable method to test the HF content of the battery's electrolyte.
The density of a liquid depends on its molecular composition. A quick density check with a METTLER TOLEDO Density Meter can help to reveal electrolyte contaminations with water or other impurities.
Conductivity measurement is an important parameter for monitoring the quality of electrolytes in a lithium-ion battery. It determines the rate at which a cell can be charged or discharged.
Differential Scanning Calorimetry (DSC) is used in QC to study the composition and content of carbonates in electrolytic solutions, which have important implications for the cycling stability, energy density and safety of lithium ion batteries. DSC also provides information on electrolyte melting and crystallization for determining the minimum temperatures for charging/discharging processes.
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The performance and safety of electrodes is largely influenced by charge/discharge induced ageing and degradation of cathode active material.
Providing precise measurements for heat capacity, decomposition temperatures and enthalpy determination, thermal analysis techniques are fundamental aids in thermal stability studies for lithium ion battery characterization. To acquire more information about degradation components from a single experiment, a METTLER TOLEDO TGA or TGA/DSC can be hyphenated to a suitable gas analysis system to perform, for example, Fourier transform infrared spectroscopy, mass spectroscopy, gas chromatography–mass spectroscopy or micro gas chromatography–mass spectroscopy.
Controlling the pH of cathode material has a significant impact on its particle size distribution and ultimately affects performance. Proper monitoring of the pH of the cathode slurry and its components during production is critical for manufacturers to ensure consistent and optimal quality.
Similarly as done for the electrolyte, cathode and anode testing includes analysis of water content prior to using the components in the battery. METTLER TOLEDO's InMotion KF Oven Autosampler heats the solid material to elevated temperatures, extracts its water and guides it to a Coulometric Karl Fischer Ttitrator, where it is detected.
Furthermore, titration can be used to determine the metal content (eg. cobalt, managenese, iron, nickel) of cathode material as well as to test the material for impurities such as chlorides, hydroxides and carbonates.
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Application notes:
Separators for Li-ion batteries have a crucial impact on battery performance, life, as well as reliability and safety. For example, degradation of separator material is frequently the root cause of an internal short circuit leading to cell failure. Thus, reliable methods for separator testing and analysis are very important.
Thermal analysis is used to characterize the thermal properties of separators, typically made from polyolefins such as PP or PE. Technological limitations of such membranes include penetration resistance, shrinkage and meltdown. These properties can be investigated by means of Thermogravimetry (TGA), Differential Scanning Calorimetry (DSC) and Thermomechanical Analysis (TMA).
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From starting materials to a high-quality product, a lithium ion battery has to run through up to 25 production steps, which lay the foundation for the demanded quality and performance. Weighing including moisture content determination is key to providing consistency and traceability along the full manufacturing chain.
Expensive raw materials represent up to 60% of the overall cell production costs. Weighing is the most accurate method of meeting high process tolerances for consistency in formulation and avoiding expensive waste.
After the electrodes are stacked, weighing is the solution for electrolyte filling. Even if it is possible to control the electrolyte flow, the accuracy of high-precision weighing devices can ensure 100% quality control.
Missing or hidden parts, that may fall into the module by accident could cause a fire and destroy it. This can be prevented by using a high-resolution scale for a completeness check, which even eliminates detection issues linked to shiny surfaces.
As the solid content of electrode slurries affects the coating quality and therefore electrode performance, strict control of solid respectively moisture content during electrode production is critical. This can be done fast and easily with a halogen moisture analyzer.
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Case studies:
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Battery performance depends to a large extend on Cathode Active Material (CAM) purity and particle size of the precursor material, PCAM.
During precipitation/crystallization, continuous control of process pH is highly important to influence the PCAM particle morphology and distribution. Process variability can dramatically change the morphology profile and is therefore undesired. Accurate inline pH measurement is prerequisite to sustain process consistency.
Precipitating PCAM (metal hydroxides) can cause scale build up on process sensors, leading to measurement drift. METTLER TOLEDO's InPro 4260i intelligent process pH sensor is tailored for PCAM manufacturing processes. Combined with the EasyClean 200 automated cleaning system, METTLER TOLEDO offers the ultimate measurement solution for reliable PCAM process pH control.
The reactor (crystallizer) requires a low oxygen level to avoid oxidation of PCAM. The InPro 6850i G is METTLER TOLEDO's small footprint in situ oxygen sensor that accurately measures O2 levels in the reactor headspace, allowing fast control of inert gas.
For NCM-type cathodes, CAM production involves calcination, during which the oxygen concentration should be precisely controlled. The GPro 500 tunable diode laser (TDL) oxygen analyzer is well suited for this application as it is specially designed to deal with the high temperature, varying gas composition, moisture content, and dust conditions found in the calciner off-gas.
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Guide: Lithium-Ion Battery Lifecycle
Ensure performance and safety along the battery value chain: Optimize processes and leverage high precision to ensure battery performance and safety.
Instruments
FAQ
What Is Lithium Ion Battery Testing and How Does it Work?
Select your question of interest:
- What is the advantage of lithium ion batteries?
- What is the life of a lithium ion battery?
- What is the safe operating temperature for a lithium ion battery?
- What is the influence of water inside a lithium ion battery?
- Which battery components need to be tested for water?
- Should the electrolyte be tested for both water and hydrofluoric acid before it is filled into the battery?
- What is the method of choice to test the electrolyte for water?
- Which method is recommended to test the solid cathode, anode and separator for water?
- Should the density of the electrolyte be checked?
- How can thermal analysis contribute to the safety investigation of lithium ion batteries?
- How can the synthesis of graphene anode material be investigated by simultaneous thermal analysis?
- Why is separator shut down important and how can it be investigated?
- Could aggressive material harm the measurement device used to formulate a slurry batch?
- How do I calibrate an industrial scales in my machinery and production system?
- What is the Benefit of weight based electrolyte filling?
- How accurate can you measure the electrolyte filling process?
- Can I detect hidden parts in battery modules with an industrial scale?
- Why is accurate process pH control important during PCAM manufacturing?
- How can I avoid PCAM degradation in crystallizers?
- During PCAM calcination, how can I be sure oxygen concentration is at the required level?
1. What is the advantage of lithium ion batteries?
Lithium ion batteries can be recharged hundreds of times and are more stable. They tend to have a higher energy density, voltage capacity and a lower self-discharge rate than other rechargeable batteries.
2. What is the life of a lithium ion battery?
The typical life of a lithium ion battery is about two to three years or 300 to 500 charge cycles, whichever occurs first.
3. What is the safe operating temperature for a lithium ion battery?
Lithium ion batteries perform optimally when charged between 0 °C to 45°C. The optimum discharge temperature is between –20 °C to 60 °C.
4. What is the influence of water inside a lithium ion battery?
The water inside a lithium ion battery reacts with the electrolyte to casuse detrimental products like hydrofluoric acid (HF). These chemicals lead to a degradation of the electrodes, disturb the overall function and ultimately lower the capacity. Moreover, water can lead to a thermal runaway scenario, leading to an explosion of the battery.
5. Which battery components need to be tested for water?
All battery components needs to be tested for water before they are built into the battery. All components that are in contact with each other via the liquid electrolyte.
6. Should the electrolyte be tested for both water and hydrofluoric acid before it is filled into the battery?
Hydrofluoric acid (HF) is known for having a bad influence on the battery's performance. It is formed through a reaction of the electrolyte with water. This reaction can occur inside a battery, but also during the production of the electrolyte. Thus, it is important that the electrolyte is not only tested for water, but also for HF itself before it is filled into the battery housing.
7. What is the method of choice to test the electrolyte for water?
Coulometric Karl Fischer (KF) titration is the method of choice to determine low water content in samples such as electrolytes. The analysis is fast, reliable and no sample preparation is needed at all. The electrolyte sample is injected into the titration vessel and the result is obtained after 1-2 minutes.
8. Which method is recommended to test the solid cathode, anode and separator for water?
Solid samples cannot be directly injected into a Karl Fischer titration vessel. So, a gas-phase extraction oven is needed to extract the water first. The InMotion KF oven automatically heats the solid sample to elevated temperatures and a stream of dry nitrogen carries the vaporized water to the coulometric titration cell, where it is detected. The analysis is fully automated. The electrode is filled into the vials and the method is started by OneClick™.
9. Should the density of the electrolyte be checked?
The density of a liquid is dependent on its composition. Water and other impurities change the density of the electrolyte. A quick density check of the electrolyte can reveal contaminations and bad quality.
10. How can thermal analysis contribute to lithium ion battery safety testing?
Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are valuable tools for determining the thermal stability and decomposition profile of the different battery components. Thermal runaway of the battery can also be investigated in both normal and extreme situations.
11. How can the synthesis of graphene anode material be investigated by simultaneous thermal analysis?
A simple and inexpensive route to obtain graphene is to reduce graphene oxide, which can be easily be obtained from graphite. The stepwise reduction of graphene oxide can be easily followed by TGA/DSC.
12. Why is separator shut down important and how can it be investigated?
For safety purposes, it is important that the separator shuts down (i.e. pore closure) before the onset of melting. This can be confirmed by thermomechanical analysis (TMA), which characterizes the shrinkage and melting behavior of the separator membrane.
13. Could aggressive material harm the measurement device used to formulate a slurry batch?
Weigh modules and load cells are typically installed on the outside of a tank or mixer, so that the measurement device has no direct contact with hot, cold, aggressive or explosive materials. In addition, these sensors are accurate regardless of shape, surface, Di-Electricity, Reynolds Number, viscosity or any other material characteristics.
14. How do I calibrate an industrial scales in my machinery and production system?
The load cells and weigh modules that are integrated in machinery and production systems are crucial components that must perform safely and accurately. METTLER TOLEDO offers tailored calibration services for every capacity to help ensure consistent results and reliable operations. These services include, Test Weight Calibration, Test Weight and Material Substitution Calibration, RapidCal™ Hydraulic Calibration ,and CalFreePlus Weightless Calibration with POWERCELL®.
15. What is the benefit of weight based electrolyte filling?
Filling the electrolyte directly on top of the weighing device enables a closed loop between the sensor and the filling device. That means you are able to constantly adjust the filling device during full production, eliminating uncertainty factors and guaranteeing a consistent battery cell quality.
16. How accurate can you measure the electrolyte filling process?
When it comes to choosing weighing technology for electrolyte filling, important parameters such as readability, repeatability and sensitivity, must be your top considerations. Most importantly, avoid using resolution as your sole selection criteria, as this alone will not guarantee stable results or high quality.
17. Can I detect hidden parts in battery modules with an industrial scale?
It is possible to perform a so called tare and cross weight check at the end of the battery module assembly. With this procedure you are able to check if all products are on board and nothing has fallen into the module during the assembly. In addition, weighing is not influenced by shiny aluminum surfaces.
18. Why is accurate process pH control important during PCAM manufacturing?
The process pH directly affects the particle size and morphology and as such is responsible for the battery performance; charging/discharging.
19. How can I avoid PCAM degradation in crystallizers?
The presence of oxygen in reactors during PCAM synthesis can easily lead to the formation of undesired NCM oxides; therefore, maintaining an inert atmosphere in the reactor headspace is important. Continuous, in situ oxygen measurement provides immediate notification of air ingress or insufficient nitrogen blanketing.
20. During PCAM calcination, how can I be sure oxygen concentration is at the required level?
Measuring O2 in a PCAM calciner’s vent line is tricky due to high temperatures, moisture, and dust. The GPro 500 in situ (or in an extractive configuration) oxygen analyzer tolerates such conditions and provides accurate measurements for enabling rapid process control.