A lithium-ion battery is comprised of four main components – cathode, anode, separator, and electrolyte. In a working battery, lithium ions flow from the anode to the cathode during discharge. The lithium-ions flow in the reverse direction during recharging. Each individual battery cell outputs only a limited amount of energy and is often combined with other cells to form battery packs. Battery packs can in turn be combined to form battery modules for energy storage applications that require higher amounts of energy output such as electric vehicles and grid storage. The materials comprising the cathode, anode, separator, and electrolyte together help define a battery’s six primary performance characteristics – run time, safety, cycle life, power, energy density, and costs.
A key aspect of selecting the best materials for each part of the battery to optimize the six primary performance characteristics depends on advanced analytical characterization. One of the most critical parameters in material selection is thermal tolerance because the materials comprising a working battery must work within a temperature range of -20 °C to 60 °C. The analytical technique known as thermal analysis is ideal for testing thermal tolerances and stability of battery materials. With thermal analysis, it’s possible to obtain such thermal parameters as the decomposition temperature, chemical composition, degree of oxidation, solvent composition, melting temperature, glass transition, and thermal stability. When thermal analysis is combined with mechanical testing, it’s possible to understand dimensional stability of a polymer’s length and shape, e.g., the polymer separator. This thermal and dimensional insight can help prevent separator failure and ensure battery safety. Finally, when it comes to putting all the materials together during manufacturing, it often requires working with slurries of solid particles, binders, and solvents. At this stage, rheology provides insights into battery slurries at each manufacturing stage including storage, mixing, coating, and drying. A rheological profile measurement can help ensure a uniform, defect-free coating that leads to production of consistent, high-quality electrodes with high batch-to-batch repeatability and low scrap rates. Putting this all together means that advanced analytical characterization of the materials comprising the main battery components for thermal, rheological, calorimetric, and mechanical properties can lead to better performing and safer batteries.