In the coming decades, the transition to green energy will necessitate a corresponding increase in battery production and innovation. Lithium-ion batteries will become the mainstay of the green energy revolution in the near future, storing energy for virtually everything, from electric vehicles and airplanes to homes and commercial buildings.
There are three types of lithium-ion batteries: cylindrical, pouch, and prismatic (also known as battery cans). Smartphones typically use pouch batteries, while most household appliances use cylindrical batteries.
Global battery production is rapidly increasing. Tesla built its first Gigafactory in Sparks, Nevada, in 2015 to produce batteries. Another Tesla Gigafactory, located in Buffalo, New York, began operations in 2017, primarily producing solar cells. The company plans to open two more factories in Berlin, Germany, and Austin, Texas, in the coming years. European battery company Northvolt also plans to begin large-scale construction of a Gigafactory in Skellefteå, Switzerland, in 2021.
The transition to green energy offers a long runway for new industries in the global economy. Manufacturing will benefit from increased demand for solar cells and batteries, and the industrial ecosystem will evolve with the development of new technologies, supporting rapid growth and high productivity in manufacturing. Lithium-ion batteries are currently at the forefront of both ecological and economic revolutions.
How are lithium-ion batteries manufactured?
While the importance of lithium-ion batteries is self-evident, their structure is conceptually quite simple. Structurally, lithium-ion batteries consist of alternating stacked cathode (positively charged) and anode (negatively charged) electrodes, each separated by a separator. Liquid or solid electrolyte is injected between the electrodes to facilitate energy transfer between the cathode and anode.
The structure of lithium-ion batteries. Compared to metal batteries, lithium-ion batteries are more stable during operation and charging. Lithium-ion batteries typically have twice the energy density of nickel-cadmium batteries, but they tend to be heavier than other batteries.
Cathode plates are typically made of aluminum foil, while anode plates are typically made of copper foil. Each plate is coated with a specific material to improve conductivity, efficiency, and adhesion.
Active materials: These determine the capacity, voltage, and characteristics of lithium-ion batteries. Cathode active materials typically include lithium cobalt oxide, lithium manganese oxide, or lithium iron phosphate. Anode plates are usually coated with some kind of carbon material, such as graphite or lithium titanate.
Adhesive: Used to adhere mixtures to foil.
Solvent: Promotes mixing of materials in the slurry, enabling the mixture to be coated onto the electrode sheet.
In addition, the cathode contains a conductive agent to reduce the battery's internal resistance and improve its conductivity.
The separator between the electrodes is made of a porous polyolefin film material coated with an aromatic polyamide layer and then cut to specific dimensions. Once the electrode sheets are stacked, they are placed into the battery casing in one of three main forms (cylindrical, pouch-shaped, or square). Depending on the battery's shape and characteristics, the battery casing will include external positive and negative terminals (for connection to the powered device), an insulating layer between the casing and the electrode stack, gaskets, vents, and other components.
Cylindrical batteries were among the first mass-produced lithium-ion battery types. They are made by stacking and winding an anode, separator, and cathode in sequence. Cylindrical batteries are well-suited for automated production, and their shape allows them to withstand higher levels of internal pressure without deformation. Cylindrical batteries are commonly used in medical devices, laptops, electric bicycles, and power tools, and are a component of Tesla's massive battery packs.
Using cameras to ensure the quality of lithium-ion batteries
Although conceptually lithium-ion batteries are simple to manufacture, consisting of coated electrode stacks and an electrolyte solvent, the actual production process is quite complex and sensitive. The thickness of the electrode coating has a significant impact on the battery's performance and even its stability.
Line scan cameras employing machine learning algorithms can facilitate automation and optimization during the quality assurance phase of lithium-ion battery manufacturing. For example, Teledyne DALSA's Linea series cameras can be installed on factory production lines and move freely during manufacturing to monitor material production. Line scan cameras are ideal for inspecting electrode sheets, as the processes from winding to coating to stacking all occur at high speeds.
Laser profilometers for inspection cameras can cover the entire manufacturing process of lithium-ion batteries. These cameras can measure the thickness of electrode sheets and coatings, find surface defects on electrode sheets such as dents, scratches, or bent edges, measure the dimensions of battery cases for cylindrical or pouch cells, and monitor the welding quality of external battery terminals.
The development potential of lithium-ion batteries
The ratio of electric vehicle sales to internal combustion engine vehicle sales can often predict the dividing line for lithium-ion battery growth rates. It is projected that by 2025, electric vehicles will account for 10% of vehicle sales, rising to 28% in 2030 and 58% in 2040. For example, California, the most populous state in the US and one of the world's largest economies, aims to have all new cars and passenger vehicles sold in the state achieve zero emissions by 2035.
Because battery storage typically occurs in pairs with renewable energy sources, growth in one directly foreshadows the adoption of the other. According to the U.S. Energy Information Administration (EIA), 70% of new energy production capacity in the U.S. will come from renewable sources in 2021 (39% from solar and 31% from wind). Therefore, battery storage capacity will also increase that year, quadrupling compared to previous years. The world's largest solar cell will be operational in Florida by the end of 2021.
Battery manufacturers need to prepare for future demand for lithium-ion batteries. The use of line scan cameras, laser profilometers, and machine learning will help battery manufacturers optimize quality assurance processes and improve efficiency.
