Unleashing the potential of battery analytics – battery applications

Maximising the efficiency and safety of batteries

In a world increasingly characterised by energy dependency, batteries play a crucial role in a sustainable future. Our precise analytical tools are designed to improve the efficiency and safety of batteries while extending their useful life.

The advanced technologies aim to push the boundaries of what is possible in battery analytics while contributing to a greener world. The aim is to explore how batteries can perform better, last longer and be safer.

Technological advances and advantages based on the development of car and mobile phone batteries

Introduction to the cell chemistry of batteries

Cell chemistry is the fundamental principle behind the functioning and performance characteristics of batteries. It comprises a complex interplay of electrochemical processes and material sciences that form the basis for energy storage and release.

In this interplay, the main components of a battery – cathode, anode, electrolyte and separator – act in a finely tuned manner to store and efficiently release electrical energy.

The cathode and anode, the electrochemical counterparts in a battery cell, determine key parameters such as cell voltage, energy capacity and cycle stability through their material-dependent redox properties.

Materials for the cathode, such as lithium cobalt oxides or lithium iron phosphate, and anode materials, including graphite and silicon-based composites, are the subject of intensive research in order to achieve optimum properties in terms of energy efficiency and density.

The electrolyte, an essential component for the transfer of ions between cathode and anode, significantly influences the ion dynamics and thus the overall performance of the battery.

The development of innovative electrolytes that ensure efficient ion transfer and at the same time increase the thermal and chemical stability of the battery is a central field of research.

This includes the investigation of both liquid and solid electrolyte formulations. The separator, a microporous layer that spatially separates the cathode and anode, is crucial for preventing internal short circuits.

Its permeability and mechanical integrity are crucial for the safety and longevity of the battery. An advanced separator design helps to improve ion diffusion and minimises the risk of thermal destabilisation.

The latest research approaches in battery technology, such as the development of solid-state electrolytes and lithium-sulphur batteries, aim to push the boundaries of conventional lithium-ion technologies.

Unlike conventional lithium-ion batteries, which use liquid electrolytes, solid-state electrolytes are made of a solid material that can still conduct ions.

These solid-state electrolytes eliminate many of the disadvantages of liquid electrolytes, such as the risk of leakage or flammability.

The advantages of solid-state electrolytes include:

1. Increased energy density: By using solid-state electrolytes, the battery can store more energy in a smaller area, resulting in higher energy density.

2. Improved safety: Solid-state electrolytes are typically non-flammable, thus reducing the risk of battery fires and thermal runaway.

3. Longer lifespan: Solid-state electrolytes are less prone to degradation over time, leading to a longer battery lifespan.

4. Faster charging times: Some solid-state electrolytes enable faster ion movement, which can result in shorter battery charging times.

Solid-state electrolytes are currently still largely in the research and development phase, but show the potential to significantly improve the performance and safety of batteries and push the boundaries of current lithium-ion technologies.

To summarise, cell chemistry is a key component in the development of advanced battery technologies. The continuous research and optimisation of electrochemical processes and material interactions within the battery cell is crucial for the realisation of more powerful, safer and more sustainable energy storage solutions.

Introduction to the cell chemistry of batteries

The performance and safety of lithium-ion batteries depend significantly on the quality and properties of their material components. Therefore, precise characterization of these components is crucial to make batteries more efficient, durable, and safer.

In this optimization process, advanced measuring devices play a key role. The cathode, anode, separator, and electrolyte can be precisely examined using the wide LINSEIS product portfolio and devices such as the DSC, calorimeter, or coupling with a mass spectrometer to gain detailed insights into the processes occurring during the charging and discharging of storage materials.

This detailed understanding enables targeted optimization of these components, thereby significantly enhancing the efficiency, lifespan, and safety of batteries.

Cathode: In batteries, the cathode plays a central role as it directly determines the energy capacity and thus the performance of the battery. It is the positive electrode of the battery and is where ions are absorbed during the discharge process, leading to the release of energy.

• Material Composition: Modern cathodes consist of various compounds such as lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), lithium nickel manganese cobalt oxide (NMC), and others.

• Crystal Structure: The crystal structure of the cathode material plays a crucial role in the battery’s performance. It influences the mobility of ions within the material and thus the rate of charge and discharge.

• Electrochemical Stability: The electrochemical stability of the cathode is crucial for the battery’s lifespan. Materials with high electrochemical stability are less prone to capacity-degrading reactions during the charge/discharge cycle.

• Surface Chemistry: The surface chemistry of the cathode material can influence its interaction with the electrolyte, thereby affecting the performance and stability of the battery. Optimizing the surface chemistry can contribute to improving energy density and cycle life.

• Thermal Conductivity: The thermal conductivity of the cathode in batteries is crucial for thermal management to prevent overheating and potential safety risks. High thermal conductivity allows efficient dissipation of heat generated during operation, stabilizing the temperature and avoiding uncontrolled temperature rise, such as thermal runaway. Therefore, selecting cathode materials and structures with good thermal conductivity is crucial for the performance and safety of battery systems.

Example – TGA Analysis of Lithium Iron Phosphate (LiFePO₄) for Cathode Characterization:

A notable example of TGA’s application is the investigation of lithium iron phosphate (LiFePO₄), a widely used cathode material in lithium-ion batteries.

LiFePO₄ is known for its high thermal stability and safety. During the TGA analysis, a sample of LiFePO₄ is gradually heated to evaluate its thermal stability and composition.

Throughout the heating process, weight changes of the sample are precisely measured to obtain information about thermal decomposition processes. This data is crucial for understanding the material’s thermal properties, which is significant for applications in areas such as electromobility or stationary energy storage.

The TGA results provide valuable insights into the stability of the cathode material under operating conditions. For instance, analyzing the decomposition temperatures of LiFePO₄ can provide insights into the battery’s lifespan and safety under various operating conditions.

This allows for targeted optimization of the material composition and cell design to enhance the overall performance and safety of the battery. The precise characterization of cathode materials through thermogravimetric analysis is thus an indispensable step in improving the performance and safety of lithium-ion batteries. Such analyses significantly contribute to the advancement and optimization of this key technology.

Anode: In batteries, the anode serves as the negative pole and is crucial for the charging speed and capacity of the battery. During the charging process, ions from the cathode are stored in the anode, with the anode playing a key role in the storage and release of these ions.

• Material Selection: Traditionally, graphite is used as anode material due to its ability to efficiently store ions. However, recent research explores alternative materials such as silicon, lithium titanate, and various carbon nanomaterials, which can offer higher capacity and faster charging speeds.

• Surface Structure and Porosity: The microstructure and porosity of the anode materials are crucial for ion storage. An optimized structure enables efficient ion mobility and contributes to higher charge capacity.

• Electrochemical Stability: The stability of the anode materials during charging/discharging cycles is essential for the battery’s lifespan. Materials resistant to electrochemical degradation enhance the battery’s cycle life.

• Interaction with the Electrolyte: The chemical interaction between anode material and electrolyte influences the battery’s performance. Optimal compatibility reduces unwanted side reactions that can lead to capacity loss.

Example – STA Analysis of Graphite Anode Materials:

A concrete example of STA application is the investigation of graphite anode materials. Graphite is commonly used in lithium-ion batteries and is known for its ability to efficiently store lithium ions.

During STA, the graphite anode material is simultaneously subjected to differential thermal analysis (DTA) and thermogravimetric analysis (TGA). This combined analysis provides valuable information about the thermal and mass-changing reactions of the material during heating.

The DTA component measures heat flow to identify endothermic and exothermic events, while the TGA records the material’s weight loss, allowing conclusions about decomposition temperatures and processes.

Through this comprehensive analysis, critical information about the stability of the anode material under various operating conditions can be obtained. For example, identifying the temperature at which the graphite begins to oxidize allows optimization of the battery management system to avoid overheating and increase battery life.

Furthermore, insights into the structural stability of the material and its impact on cycle life can be gained by examining the thermal expansion and contraction of the graphite during lithium ion intercalation.

The intercalation of lithium ions into the graphite anode material is a process where lithium is inserted between the graphite layers, resulting in a volume change. This volume change can be precisely determined using dilatometry, a method for measuring the length change of materials as a function of temperature.

A dilatometer is the device that captures the thermal expansion and contraction of graphite during lithium intercalation, providing insights into the structural stability of the anode material.

The use of simultaneous thermal analysis for investigating anode materials is also an essential step in increasing the efficiency and lifespan of lithium-ion batteries.

These in-depth analyses are crucial for developing optimized materials to meet the requirements of modern battery technologies.

Separator: In batteries, the separator plays a crucial role in safety, particularly regarding the risk of short circuits and thermal runaways. It is a microporous membrane placed between the cathode and anode to prevent direct contact and thus electrical shorts between the electrodes. At the same time, it allows ion flow between the cathode and anode during the charge and discharge cycles.

• Ion permeability: The separator must have high ion permeability to enable efficient ion transfer. This is crucial for the overall performance of the battery.

• Thermal and mechanical stability: The separator must be thermally and mechanically stable under the battery’s operating conditions. Inadequate thermal stability can lead to the separator melting and causing a short circuit, posing a significant safety risk.

• Ceramic coatings: Modern separators are often coated with ceramic particles to enhance thermal stability. These coatings increase the melting integrity and mechanical robustness of the separator, especially at high temperatures, significantly enhancing battery safety. The melting integrity of a battery separator can be characterized using a thermomechanical analyzer (TMA) to ensure the separator does not mechanically fail or tear, which could lead to thermal runaway of the battery.

• Analysis methods: To evaluate separator properties, an electromechanical measurement method is employed. These methods can provide insight into the size change of the separator under various operating conditions and the temperature at which the separator begins to fail.

• Role in preventing thermal runaway: An efficient and safe separator is crucial to minimize the risk of thermal runaway. It must maintain adequate barrier properties even when the battery is exposed to extreme temperatures.

Example – TMA Measurement of Coated Separator Membranes:
A relevant example of the application of Thermomechanical Analysis (TMA) is the investigation of separator membranes coated with ceramic particles. This coating can significantly enhance battery safety by improving the melting integrity and mechanical robustness of the separator above its melting point.

During Thermomechanical Analysis (TMA) of battery separators, the primary focus is on measuring the material’s physical response to temperature-induced changes. The central parameters measured include the expansion or contraction (strain or shrinkage) of the separator material as a function of temperature.

The TMA measurement involves the following aspects:

1. Measurement of Expansion Coefficients: The TMA measures how the separator membrane physically changes under controlled temperature conditions. This includes the linear expansion or contraction of the material with temperature changes, providing insights into the thermal expansion coefficients.

2. Evaluation of Mechanical Integrity: Measuring the strain or shrinkage of the separator at different temperatures allows for the assessment of its mechanical integrity. This is crucial for understanding how the separator reacts under the thermal conditions of battery operation.

3. Determination of Melting Point: In addition to expansion, TMA can also be used to determine the melting point of the separator material. The melting point is a critical temperature at which the separator begins to lose its structural integrity, posing safety risks.

Electrolyte: In batteries, the electrolyte is a key component essential for ion transport between the cathode and anode. In the most common scenario, it consists of a lithium salt solution in an organic solvent, facilitating the movement of lithium ions during the battery’s charging and discharging processes.

• Ionic Conductivity: The conductivity of the electrolyte is crucial for the efficiency of ion transfer between the electrodes. High ionic conductivity enables rapid battery charging and discharging, enhancing overall performance.

• Chemical Composition: The chemical composition of the electrolyte, particularly the type of lithium salt and solvent, influences the electrochemical properties of the battery. The choice of components directly affects factors such as operating voltage, temperature stability, and battery safety.

• Electrochemical Stability: The electrolyte must be electrochemically stable to avoid decomposition at the battery’s operating voltages. An unstable electrolyte composition can lead to undesirable side reactions that affect battery performance and lifespan.

• Interaction with Electrode Materials: The interaction of the electrolyte with electrode materials is crucial for the long-term stability of the battery. Optimal interaction minimizes the formation of harmful surface layers on the electrodes known as the “Solid-Electrolyte Interphase” (SEI).

• Thermal Stability: The thermal stability of a battery electrolyte is a critical factor that significantly influences battery operational safety and performance. High thermal stability of the electrolyte ensures that even under increasing operating temperatures or external thermal stresses, the chemical integrity of the electrolyte and thus the ion conduction capability are preserved. Measuring thermal stability, typically performed using a Dynamic Differential Calorimeter (DSC) or Thermogravimetric Analysis (TGA), enables the identification of temperature limits within which the electrolyte is stable and does not release hazardous decomposition products. This is essential to minimize safety risks such as thermal runaway and ensure a safe operating environment for the battery.

Example – TGA-MS Measurement of Electrolytes:
A concrete example of the application of TGA is the investigation of the thermal stability and composition of electrolytes in lithium-ion batteries.

During this measurement, the electrolyte is subjected to controlled temperature increases to analyze its thermal decomposition and resulting weight losses. These data are particularly informative for understanding the stability of the electrolyte under various operating conditions.

For instance, the decomposition temperature of the electrolyte can indicate at which temperatures the battery can be safely operated without the risk of thermal degradation of the electrolyte. Thermal degradation of the electrolyte is a process where the electrolyte decomposes under high temperatures.

This can be critical for several reasons:

1. Decomposition Temperature: Determining the decomposition temperature of the electrolyte provides insights into the temperatures at which the battery can be safely operated. The decomposition temperature is the threshold at which the electrolyte begins to chemically change and degrade.

2. Risk of Thermal Degradation: Exceeding the decomposition temperature can render the electrolyte unstable, leading to chemical reactions that impair battery performance and safety. This can also result in the generation of gases and potential pressure buildup within the battery cell.

3. Impact on Battery Performance: Thermal degradation of the electrolyte can reduce ionic conductivity and thus lead to reduced battery efficiency. Additionally, degradation of the electrolyte can lead to the formation of harmful products that affect electrode surfaces.

4. Safety Considerations: The thermal stability of the electrolyte is crucial for the overall safety of the battery. Thermal degradation can increase the risk of thermal runaway, especially if it reacts with other battery components. Furthermore, TGA-MS can be used to determine the composition of the electrolyte, including the content of solvents and other additives. This information is critical for optimizing the ion transport properties of the electrolyte, which in turn can positively influence battery efficiency and lifespan. The precise characterization of the electrolyte using thermogravimetric analysis provides essential insights for developing more efficient and safer batteries. The data obtained from these analyses enable targeted optimization of battery components, leading to improved overall battery performance.

Each of these components significantly contributes to the overall performance and safety of a lithium-ion battery. The precise characterization provided by Linseis’ measurement devices enables targeted optimization of these components, thereby significantly enhancing the efficiency, lifespan, and safety of batteries.

Prevention of thermal runaway – safety first

Thermal runaway, an uncontrolled rise in temperature in batteries, can lead to serious safety problems.

The analysers used to investigate the thermal and mechanical stability of battery materials are crucial to minimising the risks of such an event. They provide precise insights into the thermal stability of battery materials and help to identify potential sources of danger.

Thermal runaway occurs when the temperature within a battery cell reaches a point where the heat generated is greater than the heat released. This can lead to a chain reaction that destroys the battery or even causes fires. It is important to understand the causes of thermal runaway and take appropriate measures to minimise the risk.

Early Detection with DSC and TGA: Early detection of conditions that could lead to thermal runaway is crucial. Instruments like the Dynamic Scanning Calorimeter (DSC) and Thermogravimetric Analysis (TGA) provide important data on the thermal behavior of battery materials. They help identify critical temperature ranges where materials become unstable.

Analysis of Causes: Analyzing the causes of thermal runaway involves examining material compositions, electrolyte stability, and internal cell reactions. These analyses provide valuable insights to identify potential risk factors and develop corresponding countermeasures.

Safety Assessment: By measuring heat generation and heat management, the instruments can assess battery safety standards. This is particularly important in the development of batteries for high-performance applications such as electric vehicles or energy storage systems.

Material Optimization: Analysis results assist in selecting and developing materials that are less susceptible to thermal runaway. This contributes to improving overall safety, optimizing heat dissipation from the battery cell, and enhancing battery reliability.

Electrolyte Optimization: Electrolyte composition optimization is another important aspect supported by precise instruments. Enhanced electrolyte formulation based on analytical data can help increase thermal stability within the cell, thereby enhancing battery safety.

Cell Design Optimization: Optimizing cell design to prevent thermal runaway requires integrated thermal management based on careful material selection to efficiently regulate heat dissipation and absorption. Scientifically selected anode and cathode materials with high thermal conductivities, along with thermally stable separators and electrolytes, are crucial to avoid excessive heat generation. In addition, advanced cooling mechanisms and insulation materials contribute to heat distribution and isolation, preventing local overheating and homogenizing cell temperature. A well-thought-out cell design considering these components significantly increases battery safety and minimizes the risk of thermal runaway.

Preventive Measures through Material Characterization: Implementing preventive measures based on analysis results is a crucial step in minimizing the risk of thermal runaway. This includes optimizing cell design, improving battery management systems, and developing safety mechanisms.

Thermal management – risk minimisation and optimised thermal management for longer service life and efficiency

Efficient regulation of the operating temperature is a decisive factor for the performance and longevity of batteries. It helps to minimise the degradation of battery components and extend the overall service life.

Lithium-ion batteries have become the standard for portable electronics, electric vehicles and energy storage systems, mainly due to their high energy density and charge cycle stability.

The operating temperature is critical to the efficiency and longevity of these batteries, with the optimum temperature being between approximately 15°C and 35°C.

Temperatures above this range accelerate chemical degradation, increase the risk of thermal runaway and can lead to permanent loss of capacity.

Temperatures that are too low, on the other hand, impair ion diffusion and increase internal resistance, which reduces battery performance and increases the risk of lithium plating during charging.

Maintaining an appropriate operating temperature is therefore essential to ensure maximum performance, safety and battery life.

Various thermal management methods, such as active cooling or indirect liquid cooling, are crucial to keep the operating temperature in the optimal range to ensure the performance and safety of lithium-ion batteries.

Complexity of Thermal Management in Battery Technologies

• Thermal management in modern battery systems plays a crucial role in performance, safety, and longevity. It involves precisely regulating internal temperature conditions to ensure optimal functionality.

• Uncontrolled temperature increases can lead to irreversible damage due to chemical degradation, while too low temperatures can affect ionic conductivity and thus battery performance.

• Balanced thermal management not only ensures efficiency but also longevity and safety of batteries, especially in high-performance applications like electric vehicles and energy storage systems.

Analytical Instruments for Heat Transport Properties

• Advanced analytical instruments are used to investigate the thermal properties of battery materials. These include the Laser Flash Analyzer (LFA), the Transient Hot Bridge (THB), and the Periodic Laser Heating (PLH).

• The Laser Flash Analyzer (LFA) allows for the measurement of thermal conductivity and diffusivity, which are crucial for heat transfer within battery components.

• The Transient Hot Bridge (THB) expands the spectrum of heat analysis by measuring the thermal conductivity and thermal resistance of battery materials under real operating conditions.

• The Periodic Laser Heating (PLH) is an innovative method for rapid and precise characterization of thermal conductivity and specific heat capacity. It is essential for accurate thermal analysis and for the development of battery materials with superior thermal properties.

Significance of the TIM Tester for Efficient Heat Transfer

• The Thermal Interface Material (TIM) Tester specializes in evaluating materials used at the interfaces between battery cells and cooling components. Additionally, it can measure thermal impedance, enabling the optimization of thermal management for cell arrays.

• It precisely measures the thermal conductivity and thermal resistance of these materials to ensure optimal heat transfer from the batteries to the housing or cooling body.

• Efficient interface materials, identified and optimized by the TIM Tester, are essential for avoiding cell overheating and significantly contribute to improving the overall performance of the battery.

Visualization and Interpretation of Thermal Data

• Visualizing the data obtained through these analyses enables a profound interpretation of the thermal properties of battery materials.

• Charts depicting thermal conductivity or specific heat capacity across various temperature ranges provide comprehensive insights into the thermal management of batteries.

Effective thermal management, supported by precise measurements and analysis from Linseis’ instruments, is essential to maximise the performance, safety and lifetime of modern batteries.

Through continuous innovation in this area, we are helping to further improve the reliability and efficiency of battery technology.

The figure shows a measurement in which the LFA battery tests were carried out on a Na-ion cathode material. The thermal diffusivity and thermal conductivity reach a maximum at approx. 90 °C and then decrease relatively sharply.

Thermal stability – a key factor for reliable batteries

The thermal stability of battery materials is a crucial factor for the safety and reliability of lithium-ion batteries. Linseis’ state-of-the-art measurement equipment plays a central role in assessing and improving this important property.

The ability to accurately assess the thermal stability of battery materials is critical to ensure that modern batteries meet high safety and performance requirements. Linseis’ measuring instruments provide the necessary precision and reliability to fully assess this important property.

Fig. 2 shows a DSC measurement curve of a ceramic solid electrolyte, which is used in solid-state batteries and enables safer high-energy batteries. High temperature heat treatment is required to bond the electrolyte, electrodes and other components such as current collectors.

Device Characterisation – Precision in battery research with the battery calorimeter

A battery calorimeter is a device used to measure the heat generated by a battery during charging and discharging. This measurement, known as “reaction heat,” is an important indicator of battery performance. Reaction heat is the difference between the enthalpy (heat content) of the reactants and the products of a chemical reaction.

Battery calorimeters are used in research and development to evaluate new battery chemistries and optimize the design of existing batteries. They are also used in the manufacturing process to ensure that batteries meet performance and safety standards.

For thermal monitoring of batteries, Linseis offers a modular calorimeter (IBC). It consists of a variable number of nearly identical components and allows the investigation of various battery cell sizes. Additionally, the modules are easily scalable in their geometry.

Importance of Battery Calorimeter: The battery calorimeter measures the amounts of heat generated during electrochemical reactions inside the battery. These measurements are crucial for understanding and improving the thermal behavior and efficiency of batteries.

Applications: These devices are particularly important for the development of new battery types, such as lithium-ion batteries, where thermal stability and safety are of utmost importance. They are also used in quality control and performance testing of batteries.

Thermal Analysis and Safety: By analyzing heat generation under different operating conditions, battery calorimeters help identify and prevent potential safety risks such as thermal runaway. This is critical for the safety of consumer products.

Optimization of Battery Performance: Accurate measurement of heat generation enables optimization of the internal chemistry and construction of the battery, leading to increased energy density, improved charge capacity, and longer lifespan.

Research and Development: In research and development laboratories, battery calorimeters are used to test and evaluate new materials and technologies. The insights gained from these tests are essential for progress in battery technology.

Developed jointly with the Physikalisch-Technische Bundesanstalt:

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