Lithium (Li)-ion batteries are crucial power sources for a wide variety of important consumer products like electric vehicles, phones, and computers. Li-ion batteries (LIB) provide high energy storage and can deliver the power required to make electric vehicles competitive with older technologies.
Typical lithium-ion battery components and forms
LIBs consist of a graphite-based negative electrode, a Li transition metal oxide-based positive electrode, a separator, and a complex organic electrolyte. There are three common types of LIB forms: cylindrical, prismatic, and pouch (polymeric) cells. While the cylindrical and prismatic cell designs use a hard casing, the pouch cell case is made of a heat sealable aluminium laminated multilayer foil. The organization for worldwide standardization in the electrical and electronic engineering industry—International Electrotechnical Commission established a common nomenclature for technical battery standards, such as form type and size. For cylindrical cells, the first two digits (in mm) define the diameter and the next two digits indicate the cell height (in tenths of a mm). For instance, the indication R18650 is a cylindrical (or round) cell that is 18 mm in diameter and 65 mm in height. The indication P366509 characterizes a prismatic cell, which is 36 mm wide, 65 mm long, and 9 mm thick. Manufacturers may include other identifying information in combination with the nomenclature described above.
Mining for desired metals is an ancient human endeavor. Modern mining has adapted to the use of improved technology, analytical techniques, and automation. Now the mining, processing, waste management, and refining processes are all interrelated through sensors, autonomous equipment, and robotics.
Key analytical techniques used in modern mining and refining include inductively coupled plasma (ICP) and atomic absorption (AA) spectroscopy. ICP-optical emission spectroscopy (OES) provides quantitative measurement for the wide range of elements of interest in mining and refining. ICP-mass spectrometry (MS) provides high sensitivity for elements demanding high purity.
Obtaining the Li
The growth of applications for LIBs has spurred significant growth in the demand for Li worldwide. While Li is mined in different ways in different parts of the world, one new interesting method is being developed by Prairie Lithium of Canada . They are developing direct Li extraction technologies to obtain slurries with high concentrations of Li from the subsurface brines of the North American prairie.
Miners and refiners of Li use a range of analytical characterization tools to ensure delivery of at least 99.5 percent pure Li salts to battery producers. To quantify important impurities like other alkali metals and alkali earth elements, the key technology used during exploration and mining is ICP-OES. To obtain the high purity required from refining Li, which required greater sensitivity and precision, the key technology is ICP/MS. Impurities like these in the Li can impact both the performance and the safety of LIBs. For example, high sodium concentrations can lead to fires in LIB-powered devices.
Key analytical techniques to analyze LIB components
Modern LIBs are complex devices containing complex chemistry. Innovative analytical techniques and instruments are required to characterize these materials. Some of the most important analytical tools used in the LIB field include:
- Fourier transform infrared (FTIR) spectroscopy, with and without microscope—used to characterize degradation products and surface examination
- Gas chromatography mass spectrometry (GC/MS)—used to characterize evolved gases and carbonate composition
- ICP-OES—used to quantify elemental components
- ICP/MS—used for even more sensitive quantitation of elemental components
- Thermal gravimetric analysis (TGA)—used to determine thermal stability and decomposition profiles
- Differential scanning calorimetry (DSC)—used to study thermal properties of battery components
- Hyphenated technologies—TGA-IR-GC-MS—to combine the strengths of each analytical component
Manufacturing and producing lithium-ion batteries
Purity of all of the components of a LIB is critical prior to assembling a cell. Again, ICP analysis is needed to ensure that the raw materials going into the battery have sufficient purity for this application. Electrode structure and morphology are analyzed using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrolyte components are analyzed for purity with ICP and ion chromatography (IC). The organic solvents used in the electrolyte are analyzed by GC/MS.
After the cells are assembled and the protective layers are formed through charge and discharge cycles, decomposition products are analyzed by GC followed by thermal conductivity detection (GC-TCD). These decomposition products are important to understanding the formation of the solid electrolyte interphase and the cathode electrolyte interphase.
Recycling lithium-ion batteries
Recycling LIBs is beneficial both to keep potentially harmful chemicals out of the environment, and to provide another source of the metals required for their construction in addition to mining and refining virgin material.
After deactivation, discharge, and dismantling, old battery cells are shredded to gain access to the valuable metals and chemicals inside the cells. The materials of the recycled cells are analyzed by many of the same analytical techniques used in the construction of new cells. In addition, total reflection x-ray fluorescence (TXRF) and energy dispersive x-ray (EDX) spectroscopy can be applied to obtain compositional information about scrap materials.
In addition to the other components of the battery, fluoride salts are of special importance due to their potential to disrupt the recycling process by forming hydrogen fluoride (HF). GC, combustion IC, and liquid chromatography (LC) methods are important techniques to characterize this potential bad player. These analyses also provide a greater understanding of cell construction and chemical species that may be present in low concentrations.
The mixture of anode and cathode materials is analyzed by thermal methods, especially TGA and DSC to determine if additional thermal or extraction cleaning steps are required during the recycling process.
Once recycled materials have been obtained, they require the same sorts of characterization as virgin raw materials to ensure that new LIB cells can be constructed and used safely.