How machine vision empowers the future of lithium-ion batteries

In the next few decades, to transition to green energy, battery production and innovation must be increased accordingly. Lithium-ion batteries will become the main force of the green energy revolution in the near future, storing energy for almost everything, from electric cars to airplanes to homes and commercial buildings.

Lithium-ion batteries used in electric vehicles and solar power generation systems will become the driving force behind the green revolution.

Take the typical electric car Tesla Model S as an example, which uses more than 7,600 lithium-ion batteries. In the near future, this use of a large number of batteries will not be regarded as typical, but will be regarded as strange.

How machine vision empowers the future of lithium-ion batteries

In the next few decades, to transition to green energy, battery production and innovation must be increased accordingly. Lithium-ion batteries will become the main force of the green energy revolution in the near future, storing energy for almost everything, from electric cars to airplanes to homes and commercial buildings.

There are three types of lithium-ion batteries: cylindrical, pouch and square (also called battery cans). Smart phones usually use pouch-shaped batteries, while most home 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. Tesla’s other “super factory” is located in Buffalo, New York, and was put into operation in 2017. It mainly produces solar cells. The company plans to open two more factories in Berlin, Germany, and Austin, the capital of Texas, in the next few years. European battery company Northvolt also plans to start large-scale construction of a super factory in Skellefteå, Switzerland in 2021.

The transition to green energy provides a long runway for new industries in the global economy. As the demand for solar cells and storage batteries increases, the manufacturing industry will benefit from them, and with the development of new technologies, the industrial ecosystem will be developed to provide support for the rapid growth and high productivity of the manufacturing industry. Lithium-ion batteries are currently at the forefront of the ecological and economic revolution.

How are lithium-ion batteries made

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

How machine vision empowers the future of lithium-ion batteries

The structure of a lithium-ion battery. Compared with metal batteries, lithium-ion batteries are more stable during operation and charging. The energy density of lithium-ion batteries is usually twice that of nickel-cadmium batteries, but they tend to be 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 batteries. The cathode active material generally includes lithium cobalt oxide, lithium manganate oxide, or lithium iron phosphate. The anode sheet is usually coated with some kind of 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 conductivity.

The diaphragm between the electrodes is made of porous polyolefin film material, which is coated with an aromatic polyamide coating and then cut to a certain size. When the electrode sheet is stacked, the electrode sheet will adopt one of the following three main forms (cylindrical, pouch or square) into the battery case. According to the shape and characteristics of the battery, the battery case will include external positive and negative terminals (to be connected to the powered device), an insulating layer between the case and the electrode stack, gaskets, vents and other components.

How machine vision empowers the future of lithium-ion batteries

Cylindrical battery is one of the first mass-produced lithium battery types. It is formed by stacking and winding anode sheets, separators and cathode sheets in order. Cylindrical batteries are very suitable for automated production, and their shape allows the battery to withstand higher levels of internal pressure without being deformed. Cylindrical batteries are commonly used in medical equipment, notebook computers, electric bicycles, and power tools, and are an integral part of Tesla’s huge battery pack.

Using cameras to realize the quality assurance of lithium-ion batteries

Although conceptually speaking, the manufacture of lithium-ion batteries is simple, consisting of coated electrode stacks and electrolyte solvents, but the actual production process is quite complicated and sensitive. The coating thickness of the electrode has a great influence on the performance and even the stability of the battery.

Line scan cameras using machine learning algorithms can help automate and optimize the quality assurance phase of lithium-ion battery manufacturing. Take Teledyne DALSA’s Linea series camera as an example. This line scan camera can be installed on a factory production line and can be moved freely during the manufacturing process to monitor the production of materials. Line scan cameras are very suitable for inspecting electrode sheets, because the process of electrode sheets from winding to coating to stacking runs at high speed.

How machine vision empowers the future of lithium-ion batteries

The laser profiler of the inspection camera 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 curved edges, measure the size of the battery case of cylindrical or pouch-shaped batteries, and monitor the welding quality of the battery’s external terminals.

How machine vision empowers the future of lithium-ion batteries

The development potential of lithium-ion batteries

The ratio of sales of electric vehicles to sales of diesel locomotives can usually predict the dividing line of the growth rate of lithium-ion batteries. It is estimated that by 2025, electric vehicles will account for 10% of car sales, and this proportion will 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 vehicles sold in the state by 2035.

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

Battery manufacturers need to be prepared to respond to the future demand for lithium-ion batteries. The use of line scan cameras, laser profilers and machine learning will help battery manufacturers optimize quality assurance processes and increase efficiency.

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