For the development, the manufacturing and the use of the most varied of batteries, knowledge of the thermal properties, safety assessment and life cycle plays a decisive role. The primary objectives of current battery design strategy include a long service life, a multitude of complete charging and discharging cycles, and a continuous release of the stored electric energy. By means of modern thermo analytical and calorimetry measuring methods, it is possible to select and optimize the materials for anode, cathode, electrolytes, separators and to optimize the cells build with these materials. The three main battery components (anode, cathode, electrolyte etc) all jointly contribute to thermal instability. Additionally, the cell voltage exasperates the thermal instability problems. Once those cells are assemble in new battery stacks, calorimetry is the best solution to study hazard & thermal safety of, i.e. lithium ion batteries. Accelerated Rate Calorimeter (ARC) enable not only to analyze life cycle efficiency and performance of these batteries, it allows also to run abuse testing: shorting, overvoltage, nail penetration, crunch tests.
The design loop of new batteries can be summarized as follow , from raw material testing , cell design, abuse testig to recycling.
Considerable efforts are currently being channeled into battery research. The target is to find new materials enabling better energy and power density as well as more efficient energy storage. This requires sophisticated instrumentation for the production and characterization of materials such as anode and cathode materials, separators, electrolytes, boundary layers.
If you develop or produce raw materials for the battery industry, you may want to:
- Characterize nano/amorphous/ poorly crystalline materials
- Understand material behavior and materials stability as a function of temperature
- Obtain the chemical identification of evolved gases (reaction, decomposition, desorption)
- Understand thermal stability of battery raw materials
- Obtain phase transformations, phase diagrams
- Obtain thermal property data for inclusion into thermal modeling programs of cells and packs
Every application has different performance requirements and constraints. No one chemistry is the right solution for all applications. Changes in components may be required as the needs of the application change and as new technologies become available. A well-designed thermal management system is critical to the life and performance of battery cells. As electrochemical devices, batteries’ performance and lifespan are affected by temperature. High temperatures increase side reactions and decomposition of interfacial boundaries, shortening battery life and increasing battery replacement costs.
Development of precisely-calibrated battery systems rely on accurate measurements of heat generated by battery cells during the full range of charge/discharge cycles, as well as the behavior during abuse testing.
If you develop or produce battery cells, you may want to:
- Understand the impact of the cell design on the battery performance
- Know the temperature at which lithium ion cells or their components can exhibit a highly exothermic reaction
- Know the amount of energy released during a reaction, the speed of the reaction and the pressure levels arising as a result of the decomposition gas formed
- Assess the impact of a nail penetration or crush testing in the battery
When a battery is charged or discharged, heat is generated and absorbed. Isothermal calorimetry in connection with battery cyclers is a smart way to charaterize the heat flow, and therefore to analyze the battery life cycle. Temperature, charge/discharge rates and the Depth of Discharge each have a major influence on the cycle life of the cells. New Battery designs (choice of new material and/or new assembly of components) can be evaluated thanks to calorimetry mesurement. The Accelerating Rate Calorimeter (ARC) equipped with a 3D sensor allows testing in an isothermal mode in complete safety for the instrument and the operator.
If you analyze a battery performance, you may want to:
- Collect accurate heat generation data from battery module
- Run in complete safety a charge/discharge test without taking any risk to destroy the instrument
- Understand if there has been any deterioration in original performance
- Obtain a performance signature over time to evaluate the effects of aging and cycling
- Evaluate physical and electrochemical design changes that could lead to better battery modules
When batteries have reached their end of life, they are collected to be either reconditioned or reused in less demanding application, or the battery is disassembled and each single component is recycled. Batteries are built with assemblies of different polymers, oxides, metallic materials. Thermal analysis is useful characterization tools in this field.
If you are in the business of battery recycling, you may want to:
- Evaluate the feasibility of physical separation of its main components
- Evaluate the efficiency of the liberation of different components when the battery is converted into fragments
- Characterize each components of the battery, when fragmented
- Characterize the nano / amorphous / poorly crystalline recycled materials
- Understand material behavior of the recycled materials stability as a function of temperature
Lithium ion battery technology offers many advantages in portable power application but one major concern is safety. Battery developers need tools which allows them to design safer batteries without compromising performance.
By means of a “worst-case scenario” (thermal runaway) scheme, adiabatic calorimetry can provide many pertinent answers, including the temperature at which lithium ion cells or their components can exhibit a highly exothermic reaction and the associated pressure. With isothermal calorimetry, information for thermal management, obtained by means of thermal runaway, can be directly obtained.
If you develop or produce raw materials for battery, design battery cells and packs you may want to:
- Investigate thermal runaway of the battery in both normal and abusive situations
- Analyze the pressure generated when the battery cell explodes in the calorimeter
- Understand at what temperature internal short circuit occurs due to the decomposition of the individual components
- Understand what happens chemically and thermally when internal short circuits produce hot spots within the cell
- Design cells which are designed to decrease the likelihood of hot spot growth and consumption of the cell
- Design, select, or specify thermal safety devices (i.e., vent, CID, PTC) based on temperature and pressure data inside a cell during thermal decomposition and to know how well these devices work in mitigating consequences of failures
- Classify individual cells with regards to their potential risks and hazards
- Run in complete safety an isothermal charge/discharge test without risk of destroying the instrument
- Reduce the likelihood of a chain reaction of cell failures due to heat transport between adjoining cells
Manganese oxide (MnO2) is often used in chemistry as an oxidizer but also, for example, as a cathode material in batteries. The STA measurement shows mass steps at approx. 600°C and 950°C which are due to the reduction of MnO2 into Mn2O3 and finally into Mn3O4. The values of 9.20% and 3.07% match exactly with the stoichiometrical values thus reflecting the high accuracy of the balance system. Endothermic DSC peaks with enthalpies of 432 J/g and 180 J/g were detected during the reduction steps. The endothermic DSC peak at 1200°C is due to a reversible structural transformation, which is observed at 1148°C upon cooling also as exothermal peak (dashed lines). (measurement with STA 449 F1 Jupiter®)
Lithium Cobalt Oxide is widely used in cathodes for Lithium Ion batteries. The stability of the cathode material is an important factor is designing inherently safer, high performing battery systems.
In this example, a sample of delithiated LiCoO2 material was removed from a coin cell and placed in a NETZSCH STA 449 F1 Jupiter® coupled to the QMS 403 C Aëolos® for analysis. The cathode material shows several discrete decomposition steps at increasing temperature rates. With the aide of the attached mass spectrometer it is much easier to understand the decomposition pathways and the underlying structure of the cathode material after cycling.
Thermal runaway of a lithium ion cell occurs when the heat-output of the cell is greater than the heat loss. The heat output of a cell’s decomposition can be measured using an adiabatic calorimeter as long as the sample sizes are on the order of a 26650 cell or smaller.
In this example we have three 18650 cells with different chemistries and different SOC. It is clear that the LiFePO4 cells show smaller reactions starting at higher temperatures. However the initial voltage and the total charge also play a role in the decomposition and these can be tested independently.