At the heart of the infinitely small
Battery manufacturing requires constant vigilance in three areas: safety, to avoid any risk of explosion or fire, hygrometry, to prevent component degradation, and temperature, to guarantee the process parameters of the formation & aging stage (first charge of the battery) and contain the rise in temperatures in the premises brought about by the thermal loads contributed by the process equipment.
The battery stores electrical energy in chemical form. Within each cell, electrons flow between a negative electrode, the anode (copper impregnated with graphite), and a positive electrode, the cathode (aluminum impregnated with nickel, cobalt and manganese), in a conductive liquid containing lithium salts, called the electrolyte. Lithium-ion batteries differ from traditional batteries in that they charge faster, last longer and have a higher energy density, leading to greater autonomy.
COMPONENTS OF A LITHIUM-ION BATTERY
Immersion in an anhydrous clean room
The production of electric batteries requires the handling of highly hazardous and explosive products, particularly in the preparation of powders, the cathode drying process with NMP evaporation or during electrolyte distribution.
To produce batteries safely, with maximum efficiency, you need a clean and dry room. HVAC (heating, ventilation, air conditioning, air treatment) solutions enable us to maintain a very low level of hygrometry (RH* less than 2%, a "dew point" of between -30 and -45°C), to prevent water from coming into contact with the sensitive metal lithium.
Each room is equipped with pressure sensors to ensure that air moves from the room to the outside and never vice versa, temperature sensors and humidity sensors. In this way, the atmosphere is constantly under control in a room with excellent airtightness and an efficient, well-dimensioned aeraulic system.
Optimized solutions
To guarantee a safe, high-performance environment for battery production, Equans designs and builds anhydrous cleanrooms that comply with the most demanding standards.
Protected by a hermetic enclosure, they are placed under continuous control and feature specific air filtration. Humidity levels remain under control, with air swept evenly throughout the room and overpressure management in relation to adjacent rooms.
As Alex Authier, Design Project Manager in the Development Department at Equans France, points out: "Filtration, like the removal of humidity, is a very energy-intensive process. Anhydrous rooms account for between 20% and 30% of a gigafactory's energy consumption." This is why, upstream of the project, Equans teams work with the customer to define the best enclosure sizing, with a view to optimizing the energy performance of the facilities. To obtain very dry air, humidity is removed by cooling, then via desiccant wheels. "Here too, we're trying to work on efficient solutions via energy recovery for the regeneration of these desiccant wheels to reduce energy consumption", adds Alex Authier. Temperature and humidity measurements enable real-time adjustment of blowing conditions to maintain the required conditions in anhydrous and clean rooms.
“ Filtration, like the removal of humidity, is a very energy-intensive process. Anhydrous rooms account for 20-30% of a gigafactory's energy consumption. ”
Ultra-technical devices for a comprehensive offering
Battery production relies on several complementary devices, including the electrolyte storage and distribution facility.
This potentially explosive solvent in contact with humidity requires handling under gaseous skies (with nitrogen, for example). In a humid environment, the lithium salt contained in the electrolyte can transform into hydrofluoric acid, damaging the product's physical and chemical properties, as well as parts of the installation. It is therefore important to ensure that the volume of electrolyte poured at the end of the battery manufacturing process has not been in contact with air humidity.
Thanks to its long-standing mastery of chemistry distribution in microelectronics, Equans is able to design, manufacture and commission electrolyte distribution and storage systems, combining performance, efficiency and safety. And all this in full compliance with the environmental and ATEX regulations of the country concerned.
Another key point in battery manufacturing concerns the NMP. Philippe Humeau, Process Engineering Manager at Equans France, explains its role: "To spread the slurry, a type of ink containing the rare metals, evenly, we use a solvent, NMP. After the process of coating this ink onto an aluminum foil, the coated strip circulates through a drying oven at a temperature of between 100 and 130°C to evaporate the solvent."
Equans has developed an innovative technology for treating the air, recovering this NMP, reinjecting the purified air into the oven and capturing any excess heat to power, for example, regeneration systems for cleanroom dehumidification devices. This NMP recycling system is the subject of a PCT patent filed by Equans.
“ A solvent, NMP, is used to evenly spread the slurry, a type of ink containing rare metals. After the process of coating this ink onto an aluminum foil, the coated strip circulates through a drying oven at a temperature of between 100 and 130°C to evaporate the solvent. ”
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