This chapter introduces materials for the cathode, anode, and electrolyte of Li-ion batteries (LIBs), which make up the structural and chemical foundations for an electrochemical battery cell. In this chapter, we will discuss the development and application of battery materials ever since the invention of LIBs in 1970s. We further investigate the advantages and disadvantages of varying battery materials from the electrochemical, structural, environmental, and safety perspectives. Afterwards, we summarize the trends for the development of next-generation battery materials to resolve the standing issues of current battery materials. Last but not the least, this chapter will present the practical design principles and limitations of battery materials, which are essential for the development and operation of battery cells.

Continuing with the concepts discussed in this text the next interconnected step in the lithium-ion battery (LIB) manufacturing process is electrode slurry application onto the metal foil current collector. This process is commonly referred to as a coating process; however, in practice, the current methods are founded and fundamentally very similar to legacy processes used in the printing, photographic film, and magnetic media industries. Those industries have all seen a decline in market demand over the last few decades while the market demand for LIB has and continues to increase. The state-of-the-art coating process has been and continues to be slot die coating, employing a variety of configurations depending on a host of process variables such as target electrode loading mg/cm², foil current collector thickness and quality, production plant layout, target coating width, and production machine speed range which is commonly referred to as the coating line speed or simply line speed.

Additive manufacturing (AM) enables the fabrication of complex shapes and formfactors that are inefficient or impossible to produce with traditional subtractive machining tools. AM emerged in the 1980s to enable the rapid creation of functional prototypes (also known as rapid prototyping). The first commercial implementation of AM was a stereolithography (SLA) system developed by 3D Systems in 1987, wherein a laser solidified thin layers of a photoactive polymer solution. In the early 1990s, fused deposition modeling (FDM), selective laser sintering, and other AM modalities began to emerge and have continued to grow in the decades since. Within the last ten years, AM has gained traction as an approach to fabricate Lithium-ion batteries (LIBs) because it enables (1) novel three-dimensional (3D) electrodes that optimize energy and power performance and (2) customizable battery shapes for integrated and mechanically robust batteries for portable device applications. As energy storage demands grow, so does the need for LIBs to come in a multitude of sizes, shapes, and materials that meet the needs of a given application. In this chapter, we review the main AM approaches that have been used to produce LIBs with a focus on FDM, direct-ink write (DIW), inkjet printing (IJP), aerosol jet printing (AJP), electrostatic spray deposition (ESD), stereolithography (SLA), and newer field-assisted (FA) methods.

Once the lithium-ion battery (LIB) electrode slurry is applied to the current collector, the solvent from the coating must be removed in the drying step. Occasionally, the qualifier "primary" is used to differentiate this step from downstream secondary drying, which is used to reduce the moisture content of electrodes. Electrode drying most commonly occurs in long convection ovens that are placed in-line with the coating apparatus. In other words, the current collector starts as a bare foil, then is coated, and fed into the drying oven all in one step without any need for switching the foil onto a new roll. Knowing the speed of the substrate, the dryer can be sized appropriately to secure that there will be sufficient time for the solvent to be removed. The synergy between coating and drying is beneficial for process efficiency but requires a high degree of tuning and quality assurance to ensure that the electrodes are being dried well.

After the electrode is dried, it is passed to a machine that reduces the thickness of the electrode. The machine, commonly called a calender and sometimes called a rolling press, consists of two rollers that are rotated in opposite directions (i.e., one clockwise and the other counterclockwise). A gap is set between the rollers that can be correlated to the desired thickness of the electrode. Since energy density is essential for LIB electrodes in many applications, calendering is a useful process for reducing excessive void space in the electrodes that contribute nothing to energy density. However, the balance between thickness/porosity and electron/ion transport, as well as the effect on electrode mechanical properties, must be considered carefully when determining the optimal calendering conditions.

Further downstream in manufacturing, typically right before the electrodes are built into a cell, a secondary drying step is often employed. This secondary drying step is necessary to keep the moisture content of the electrodes low since moisture can harm the performance and safety characteristics of the cell. However, the secondary drying step time should be minimized to avoid process bottlenecks and excessive manufacturing energy costs.

In this chapter, these three processes will be discussed. The effect of each process on the electrode microstructure and resulting electrode performance is considered, as are the characterization methods of electrodes after each stage.

The state-of-the-art lithium-ion battery (LIB) manufacturing process uses N-methyl-2-pyrrolidone (NMP) as solvent for the electrode slurry dispersing stage. NMP is a hazardous chemical, known particularly for its reproductive toxicity. NMP has been the subject of recent government action in many countries and is likely to face increasingly restrictive measures curtailing its use. In December 2020, the United States Environmental Protection Agency (US EPA) concluded its most recent risk assessment for NMP, finding that it poses an unreasonable risk of injury to health in 26 of 37 use cases, including specifically for "industrial and commercial use... in lithium ion battery manufacturing". More direct action was taken in Europe in 2020 when the European Chemical Agency imposed a restriction on May 9, 2020, banning the use of NMP in concentrations greater than 0.3% without appropriate risk management measures.

The development of clean energy technology is one most important requirements to decrease energy-related carbon dioxide emissions. This challenge triggers the development of renewable energies to scale up in the short and medium terms because of the growth of fuel prices and fossil source depletion, extreme heatwaves, and zero-emission vehicle sales by 2035. Efforts such as electrification of transportation and electricity storage are rising steadily over the past ten years by the number of patent filings in batteries and energy accumulation. The preferred battery technology is Li-ion batteries (LIBs) due to their large capacity, high power, and cyclability. Continued innovation in LIBs is needed to satisfy the electric vehicle demands, including the development of Gigafactories to decrease production costs. To address these large-scale production efforts, it is necessary to optimize further the manufacturing parameters to fabricate LIBs. Optimization efforts across the battery production requests for improved materials, cell designs, manufacturing processes, carbon dioxide emission fingerprints, and recycling. The manufacturing optimization is developed at the prototype level rather than in Gigafactories, aiming at the final product design and quality tests by a systematic trial-and-error process. This process is time and cost-consuming because the battery manufacturing process is multistep, which includes three major steps: electrode preparation, cell assembly, and formation and testing, affected by many experimental parameters.

Lithium-ion electrode manufacture is a complex multi-stage process, and so quality control is vital at each stage to maintain production speed and reduce wastage. Current electrode manufacture is based on a slurry casting process, where the dry ingredients are suspended in a minimum of solvent to form a slurry, which is coated onto a current collector, dried to remove the solvent, and the coating calendared (compressed) to a target porosity (Figure 14.1). However future technologies may include dry processing or alternative deposition methods. Quality control is performed at several key stages of the process; on the raw material components, the slurry mix before coating, the coating during deposition, after drying, and after calendaring.