Basic principles of battery
The smallest unit in a battery is the electrochemical cell, comprising of cathode and anode isolated by an electrolyte. The electrolyte acts as an insulator but conducts electrons under prescribed conditions. Under charged state, anode holds high concentration of embolismed lithium whereas cathode is depleted of lithium. During discharged conditions, lithium ions leave the anode and moves to the cathode through the electrolyte medium associated with current collector that collects electrons which has to be used as a power to electrical applications.
To establish a basic understanding of lithium battery fabrication, this blog shows the sequential processes of fabrication procedure for futuristic lithium ion batteries.
Procedural techniques for fabrication of lithium ion battery
Figure 1: Steps for lithium ion battery fabrication
Electrodes for the lithium ion batteries can be fabricated using anode and cathode which are processed using similar or identical equipment. The active electrode materials are coated using metallic foils in order to conduct the current. Anode materials are lithium, graphite, lithium-alloying materials, intermetallics, or silicon. Carbonaceous anodes are the most utilized as anodic material due to their low cost and availability. However, the theoretical capacity (372 mAh/g) is poor compared with the charge density of lithium (3,862 mAh/g). State-of-the-art cathode materials include lithium-metal oxides [such as LiCoO2, LiMn2O4, and Li(NixMnyCoz)O2], vanadium oxides, olivines (such as LiFePO4), and rechargeable lithium oxides. This material carries precautions while delivering since the contamination between the anode and cathode material will ruin the battery. So care must be taken to prevent these materials in contacting with each other. For this reason, anodes and cathodes must be processed separately with each other. Stepping procedure was given as schematic in fig.1
Figure.2 Schematic view of processing of active materials
The primary stage is to blend the anode materials with a conductive folio to frame a slurry which is spread on the surface of the foil as it goes into the machine. A blade edge is found simply above the foil and the thickness of the anode coating is controlled by altering the hole between the blade edge and the foil. Since it isn’t strange for the gravimetric or volumetric energy stockpiling limit of the anode material to be not the same as that of the cathode material, the thickess of the covering layers must be set to permit the energy stockpiling per unit zone of the anode and cathode terminals to be coordinated. From the coater, the covered foil is bolstered specifically into a long drying stove to prepare the cathode material onto the thwart. As the covered thwart leaves the broiler it is re-reeled. The covered foils are in this way encouraged into slitting machines to cut the thwart into smaller strips reasonable for various sizes of cathodes. Later they are sliced to length. Any burrs on the edges of the thwart strips could offer ascent to inside short circuits in the cells so the slitting machine must be exactly made and kept up.
Functions of Electrode coating (metallic foils)
Prevents the oxidising effects causing by atmosphere and formation foam by weld pool
Helps slag to form and removes impurities
Slag slow down cooling thus prevents the brittleness
Can contain alloying metals and additional filler metal
Cells and Modules assembly
Figure.3 Schematic view of various stages of cells and modules assembly
1. The anodes, cathodes, and separators are cut to a prescribed length, and then the components are alternately stacked in the order of anode, separator, cathode, separator, anode, etc. at a high speed using fully automated equipment. Tabs that function as the exits and entrances for electricity are also connected to each of the cathodes and anodes.
2. Electrolyte Injection and Sealing Process Next, the electrolytic solution is poured into the cell, which has been sealed with an aluminium laminate.
3. Place the charged cells in the temperature controlled room with a certain period at the specified temperature (aging).
4. The battery capacity, voltage, and other basic properties are measured.
5. For all cells, the predetermined inspection, by various points of view, is automatically conducted and the external appearance is visually inspected. The inspection data is linked to the ID attached to every cell (the photo shows a barcode with an ID recorded) and recorded.
6. After passing the final cell inspection, cells are layered, connected to external terminals and then enclosed in a metal case. After module inspection, module is completed.