Take the typical Tesla Model s electric vehicle as an example, which uses more than 7600 lithium-ion batteries. In the near future, this situation of using a large number of batteries will not be regarded as typical, but will be regarded as strange.

In the coming decades, in order to transition to green energy, we must correspondingly increase the output of batteries and improve their innovation. Lithium ion batteries will become the main force of the green energy revolution in the near future, storing energy for almost everything, from electric vehicles to aircraft, to homes and commercial buildings.

There are three types of lithium-ion batteries: cylindrical, bag and square (also known as battery can). Smart phones usually use pocket batteries, while most household appliances use cylindrical batteries.

The world’s battery production is rising rapidly. Tesla built its first “super factory” in sparks, Nevada in 2015 to produce batteries. Another “super factory” of Tesla, located in Buffalo, New York, was put into operation in 2017, mainly producing solar cells. The company plans to open two more factories in Berlin, Germany and Austin, Texas in the next few years. Northvolt, a European battery company, also plans to start large-scale construction of a super factory in skellefte å, Switzerland in 2021.

The transition to green energy provides a long runway for new industries in the global economy. With the increasing demand for solar cells and batteries, the manufacturing industry will benefit, and with the development of new technologies, the industrial ecosystem will develop to support the rapid growth and high productivity of the manufacturing industry. Lithium ion batteries are at the forefront of the ecological and economic revolution.

How are lithium ion batteries made

Although the importance of lithium-ion battery is self-evident, conceptually, the structure of lithium-ion battery is very simple. Structurally, the cathode (positively charged) and anode (negatively charged) electrode sheets of the lithium-ion battery are stacked alternately, and each layer is separated by a diaphragm. Liquid or solid electrolyte is injected between the electrode sheets to promote energy transfer between the cathode sheet and the anode sheet.

Structure of lithium ion battery. Compared with metal batteries, lithium-ion batteries are more stable during operation and charging. Lithium ion batteries usually have twice the energy density as nickel cadmium batteries, but they are often heavier than other batteries.

The cathode sheet is usually made of aluminum foil, while the anode sheet is usually made of copper foil. Each piece is coated with a specific material to improve conductivity, efficiency and adhesion.

Active material: determines the capacity, voltage and characteristics of lithium ion battery. Cathode active materials usually include lithium cobalt oxide, lithium manganate oxide or lithium iron phosphate. The anode sheet is usually coated with some carbon material, such as graphite or lithium titanate.

Adhesive: used to adhere the mixture to the foil.

Solvent: promote the mixing of materials in the slurry so that the mixture can be coated on the electrode sheet.

In addition, the cathode also contains a conductive agent to reduce the internal resistance of the battery and improve the conductivity.

The diaphragm between the electrodes is made of porous polyolefin film material, which is coated with aromatic polyamide and then cut to a certain size. When the electrode sheets are stacked, the electrode sheets will be put into the battery shell in one of the following three main forms (cylindrical, bag or square). According to the shape and characteristics of the battery, the battery shell will include external positive and negative terminals (to connect with the powered equipment), insulation between the shell and the electrode stack, gaskets, exhaust holes and other elements.

Cylindrical battery is one of the first mass-produced lithium battery types. It is composed of anode sheet, diaphragm and cathode sheet stacked and wound in order. Cylindrical battery is very suitable for automatic production. Its shape enables the battery to withstand a higher level of internal pressure without deformation. Cylindrical batteries are commonly used in medical devices, laptops, electric bicycles and electric tools, and are an integral part of Tesla’s huge battery pack.

Quality assurance of lithium ion battery using camera

Although the manufacturing of lithium-ion battery is conceptually simple, which is composed of coated electrode laminations and electrolyte solvents, the actual production process is quite complex and sensitive. The coating thickness of the electrode has a great influence on the performance and even stability of the battery.

The line scan camera using machine learning algorithm can help to realize automation and Optimization in the quality assurance stage of lithium-ion battery manufacturing. Take the linea series camera of Teledyne DALSA as an example. This line scanning camera can be installed on the factory production line and can move freely during the manufacturing process, so as to monitor the production of materials. The line scan camera is very suitable for inspecting electrode sheets because the process of electrode sheets from winding to coating to stacking runs at high speed.

The laser profiler of the detection camera can cover the whole manufacturing process of lithium-ion battery. These cameras can measure the thickness of electrode sheets and coatings, find surface defects on electrode sheets, such as dents, scratches or curved edges, measure the battery shell size of cylindrical or bag batteries, and monitor the welding quality of external terminals of batteries.

Development potential of lithium ion battery

The ratio of electric vehicle sales to diesel locomotive sales can usually predict the dividing line of lithium-ion battery growth rate. It is estimated that electric vehicles will account for 10% of vehicle sales by 2025, and then increase to 28% and 58% in 2030 and 2040 respectively. For example, California, as the most populous state in the United States and one of the largest economies in the world, aims to achieve zero emissions for all new cars and passenger cars sold in the state by 2035.

Since battery energy storage is usually paired with renewable energy, the growth of one energy directly indicates the adoption of another energy. According to the data of the U.S. Energy Information Administration (EIA), 70% of the new energy capacity in the United States in 2021 will come from renewable energy (39% from solar energy and 31% from wind energy). Therefore, the storage capacity of battery in this year will also increase, four times higher than that in previous years. The world’s largest solar cell will be put into operation in Florida by the end of 2021.

Battery manufacturers need to be prepared for the 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.

        Editor in charge: PJ

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