In today's fast-paced digital age, batteries power everything from smartphones and laptops to electric cars. As the world becomes increasingly digital, battery producers face enormous pressure to meet the demand for high-performance, safe goods.
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While advancements in battery-powered devices and solutions may make headlines, a silent hero works tirelessly behind the scenes to assure battery preservation and efficiency: the Karl Fischer Titrator.
While Karl Fischer (KF) titration is known as the champion of battery manufacturing quality control, techniques such as Loss-on-Drying (LOD) and Thermogravimetric Analysis (TGA) help it achieve its primary goal of precisely measuring the water content of battery components and electrolytes.
Unmasking the Threat
Water is the elixir for life. However, in the precision-driven world of battery manufacture, water is the challenger of lithium-ion batteries, which are the powerhouses of our modern devices. Even in small proportions, its undetectable presence can weaken the foundation of our modern energy storage technology.
Water Can Unleash Havoc in Several Ways
Performance Degradation
Water reacts with the electrolyte's conducting salt (such as LiPF6), breaking down the electrolyte and perhaps creating hydrofluoric acid. The generated hydrogen fluoride (HF) can subsequently attack and corrode the battery components, lowering performance and creating potentially hazardous situations.
Safety Hazards
During normal operation, batteries produce a tiny amount of heat as electrons flow between the anode and cathode. Internal components, such as temperature sensors or protective circuits, may fail owing to moisture or HF breakdown, resulting in a dangerous situation known as thermal runaway where battery cell temperatures rise rapidly. This can lead to a fire or an explosion.
The process begins at an apparent low temperature of 80 °C, when the protective layer on the anode (the Solid Electrolyte Interface (SEI)) begins to break down in a reaction that produces heat, sparking the following chain reaction:
- At temperatures between 100 °C and 120 °C, the electrolyte decomposes, releasing gases, including CO, CO2, CH4, C2H4, and H2 that might cause an explosion.
- At 120 °C to 130 °C, the separator component melts, resulting in an internal short circuit and increased heat generation.
- At 150 °C, the cathode reacts with the electrolyte, producing oxygen and leading to cell failure.
- If left unchecked and temperatures surpass 180 °C, the reaction becomes self-sustaining. The resultant oxygen feeds the breakdown process, generating a dangerous runaway scenario in which temperatures rise fast, perhaps leading to a battery fire or explosion.
Even small amounts of water can cause a terrible and deadly situation, necessitating rigorous investigation. Karl Fischer’s titration tool precisely detects and manages water content in lithium-ion materials, guaranteeing that minimum moisture reaches the final cell.
KF Titrator's Tactical Arsenal
Karl Fischer's innovative technique, developed in the 1930s, has stood the test of time, becoming a standard for correctly measuring trace amounts of water (ppm levels) in various samples for various sectors.
Karl Fischer titration does not operate alone. It collaborates with a trio of other extensive approaches to form an ideal team for testing liquids and water content. Together, they provide a complete view of what is happening inside your battery, ensuring it works optimally.
Coulometric KF Titration
Measuring electrode sheets is problematic due to their low water content (<30 ppm) and complicated metals, polymers, and additives composition. However, the coulometric KF oven technique is up for the job.
The procedure entails placing a vial of cut-up electrode sheet pieces in an oven at temperatures high enough to release water efficiently but not high enough to cause samples to dissolve.
A dry inert gas, commonly nitrogen, then travels through the vial and transports the moisture vapor to the titration cell, where the KF reagent reacts with the water and electrochemically produces iodine.
The current flow decreases as the water is used, and the electricity required to create iodine is proportionate to the amount of water taken. This clever mix of heat, gas flow, and chemical reaction allows precise water content analysis in these critical battery components.
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Loss-on-Drying (LOD) Method
Loss-on-drying is a simple and effective method of quality control in Li-ion battery manufacture that ensures materials have the correct moisture or solvent level.
LOD can also calculate the moisture content of active materials, such as lithium cobalt oxide (LiCoO2), and other active metal salts. Excess moisture in these components can cause undesirable side reactions during battery construction.
By carefully assessing their moisture level, LOD ensures that active ingredients react suitably, binders adhere effectively, and separators work optimally.
Perhaps most significantly, LOD addresses the "front end" of battery manufacture, namely the slurry stage, in which a paste (a combination of conductive additives, active electrode materials, binders, and a solvent) is prepared before being thinly sprayed onto the electrode.
The slurry is gradually heated to evaporate the liquid solvent and then compared to the sample weight before heating.
LOD guarantees constant electrode creation, which is critical because inadequate viscosity can result in uneven material distribution and impede the mixing process. In contrast, an overly viscous slurry can cause poor adhesion, cracking, and a shorter lifespan.
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Thermogravimetry
Thermogravimetric analysis (TGA) is a useful instrument that extends beyond determining weight changes caused by water loss during heating. It is important to understand how water is bound in a material and how it affects thermal behavior, such as breakdown and stability.
- TGA characterizes battery materials, such as anodes, cathodes, separators, and binders. Chemical engineers can learn about the temperature at which decomposition occurs, thermal stability, and purity by tracking weight changes while the material is heated to high temperatures. Understanding the rate and temperature of material decomposition allows manufacturers to create safer batteries with lower thermal runaway risk.
- Thermal analysis during Li-ion battery manufacture can also help optimize electrolyte formulation. Researchers can use TGA and evolved gas analysis (EGA) to assess weight changes and identify gases emitted during heating. For example, TGA-EGA could show that a specific salt in the electrolyte decomposes at a low temperature, generating flammable gases. Manufacturers can choose a safer electrolyte formulation by replacing salt with a more stable alternative, resulting in low gas evolution.
- TGA can more correctly distinguish between different types of water that may be present in a sample. Free or loosely bonded water evaporates at lower temperatures, whereas bound water adheres more strongly to the substance and requires higher temperatures to evaporate. This distinction is critical for assessing the stability and quality of materials, as the presence of bound water can have a major impact on their properties.
By combining these three methodologies, battery manufacturing engineers and manufacturers can fully understand a material's properties and thermal behavior. Ensuring that the water content in battery materials meets strict specifications offers several benefits.
Sustainability Through Quality
Delivering the Precision to Drive Innovation in Battery Manufacturing
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Extended Battery Life
- Mitigating Electrolyte Degradation: Controlled water content extends battery life and prevents electrolyte degradation. Maintaining proper capacity and power distribution improves battery performance and longer use cycles between charges.
Enhanced Battery Performance
- Reduced Internal Resistance: Batteries with lower internal resistance are more efficient and perform better, allowing electric vehicles to travel further on a single charge. This reduces range anxiety and supports sustainability.
Rigorous Safety Assurance
- Abating Side Reactions: Combining KF titration, LOD, and TGA reduces safety risks from water-induced side reactions, particularly volatile events. This stringent methodology promotes dependable and safe battery performance in various applications.
The Champion of Battery Manufacturers
Though Karl Fischer titration is not the most recent or unique procedure, the KF titrator is an invaluable tool for energy solution architects when combined with LOD and TGA methodologies.
This powerhouse trio assures that every lithium-ion battery that leaves the factory meets the highest quality and efficiency standards, pushing us into future generations of clean and sustainable energy.
This information has been sourced, reviewed and adapted from materials provided by Mettler-Toledo - Titration.
For more information on this source, please visit Mettler-Toledo - Titration.