Li Ion Battery Factory
Lithium-ion batteries are one of the most advanced rechargeable battery technologies available today. They offer high energy density, large capacity, low self-discharge and long service life.
Manufacturing lithium-ion batteries is a challenging process that involves sophisticated equipment and exacting technology. It is important to follow best practices throughout the production cycle.
Stage 1: Electrode Fabrication
Electrodes are an essential part of lithium ion batteries, a technology that has become the main energy storage system for portable devices and electric vehicles. They consist of active materials, conductive additives and polymer binders, all of which have specific tasks in the cell.
The manufacturing process of the electrodes is crucial in determining battery performance as it affects morphology and interface properties, which influence parameters such as porosity, pore size, tortuosity or effective transport coefficient. Among the most important preparation steps, the electrode slurry mixing and calendering are particularly important for their impact on battery performance.
In this stage, different types of conductive polymers and solvents are mixed to produce an electrode slurry which is then coated onto copper and aluminum foil using an application tool (e.g. slot die, doctor blade, anilox roller). This process helps to control the thickness of the coating and adjust the physical properties (bonding, conductivity, density, porosity, etc.).
Once the slurry is coated, it is then dried and calendared to reduce porosity and improve particles cohesion. This process improves the electrode slurry pore structure and allows for a smooth transition into the final cell.
Besides the slurry mixing and coating process, there are many other factors that impact electrode fabrication. These include the type of polymer matrix, the conductive additive, the spread method, and the heating and solvent evaporation conditions.
For example, a novel dry spray printing technique is used to make structured electrodes with higher capacity than slurry-cast electrodes. The main drawbacks of this technique are the need for solvent evaporation and a time-consuming drying process (approximately 2 hours at 400 degC).
Additionally, these electrodes are not as flexible as other 3D-printed electrodes. The structure of these structured electrodes is also not as stable.
Another method for fabricating electrodes is the screen-printing process. The main advantage of this method is that it uses cheap materials and can be made in large scale. However, this method requires solvent to be evoporated and is more complicated than the slurry-cast electrode method.
Stage 2: Electrolyte Injection
Electrolyte injection is an important step in the production of lithium ion batteries. The quality of the electrolyte and electrode materials is largely dependent on the correct filling of this critical phase of the manufacturing process.
As a result, accurate and consistent electrolyte filling is vital for the consistency of formulation and the avoidance of expensive waste material. It is also the most time-consuming step in the battery production line, as the amount of electrolyte that needs to be injected depends on the cell size and cell geometry, which requires high-precision weighing devices.
The liquid electrolyte that is injected into the battery core during the injection step is composed of a lithium salt (Li+), organic solvents such as cyclic and linear carbonates, and various additives. It is typically a water-free solution because even trace amounts of water will react with the electrolyte, leading to aggressive by-products such as hydrofluoric acid that will compromise battery performance and safety.
During injection, the confined lithium ion electrolyte is pumped into the porous electrode through a pipe containing an electric current. As this process is highly prone to gas migration, it is necessary to extract part Li Ion Battery Factory of the gas from the electrolyte before injecting it into the cell.
This extraction process is a crucial step for lithium ion batteries, as it can significantly reduce the residual gas in the pore space of the battery structure and impact its longevity and performance. However, because the gas evolution during the battery operation is dynamic and time-dependent, the amount of residual gas in the pore structure can vary.
For this reason, simulations of the ionic flow and the distribution of the residual gas in the pore space are essential for understanding the influence of various design parameters on the overall residual gas phase content of the cell. In this study, the interaction of different electrolytes with polycrystalline graphene was simulated using a quasi-static model. The capillary pressure, the weighted capillary number, and the MacMullin number were analyzed for three different electrolytes.
The results show that the interaction of the electrolyte with polycrystalline graphene is highly influenced by the contact angle of the electrode, as a higher contact angle leads to a lower contact pressure. Moreover, the weighted capillary number increases with viscosity of the electrolyte and the infilling speed, which can explain why higher viscosity electrolytes have higher MacMullin numbers than low viscosity ones.
Stage 3: Cell Assembly
The next step in the process is to assemble the lithium ion battery into cells. This is done in a variety of formats and requires several different machines to complete the job. These machines include die cutting machines, stacking machines (pouch cells), winding machine, sealing and tab welding machine, and electrolyte filling machine.
The electrode thickness is another crucial component that Li Ion Battery Factory affects the cell performance and reproducibility. This is because the thickness of the electrode determines how much spring compression there will be in the battery. It is also a factor that determines the internal applied pressure.
As a result, it is important to select the correct electrode thickness and spacer thickness. The spacer thickness should be consistent to achieve a closed internal pressure condition. This is also necessary for the proper alignment of the cathode and anode, which helps with long cycling stability.
Once the electrodes are assembled, they are then tested in a formation tester to ensure they meet the cell specifications. This is done to sort out the weaker cells and is used for quality assurance.
After the formation test, the cells are then placed on an aging rack and stored in a room for a specific amount of time. During this time, the cells are monitored for capacity and voltage changes to see if they are within the specifications.
These tests can vary between manufacturers but usually involve pulse testing, internal resistance measurements, optical inspections, OCV tests, and leakage tests. This is to ensure that the cells are in good condition before they are shipped to a customer.
Although the cell assembly is not as complex as a lead acid battery, there are still many different steps that must be completed. This is because the cell has a complicated structure that makes it difficult to open and disassemble. This is especially true in the case of large automotive battery packs, which have hundreds or thousands of cells.
Despite the complexity, the lithium ion battery is becoming one of the most popular energy storage solutions in the world. This is due to its ability to power a wide range of devices, including electric vehicles, mobile phones, and computers. With the increasing demand for lithium-ion batteries, more research must be done to optimize the cell manufacturing process to achieve better results.
Stage 4: Packaging
Packaging has an important role in battery performance and cost. It also affects the environment. It is important to know the advantages and disadvantages of different packaging types to make decisions about the best solutions.
There are many packaging types and chemistries available for lithium-ion batteries. They come in a variety of shapes and sizes and differ in their performance and capacity. The most common li-ion batteries are the cylindrical cells that are used in battery packs or modules, which are also called “pouch” cells.
The advantages of cylindrical cells are that they can be grouped in a module or pack and air can circulate through them, which reduces cooling. They are also comparatively light, which increases the packaging density.
Moreover, they are very safe for handling, since their shape allows them to withstand internal pressures without deformation. They are especially popular for light industrial use, but are not ideal for electric vehicles (EVs).
In contrast to the cylindrical cell concept, pouch cells have a higher density and lower costs because of their rectangular shape. However, they are less suitable for EVs because they lack the structural rigidity of the cylindrical cells.
Batteries are highly complex structures and require a high level of manufacturing automation in order to produce them. They require investment in equipment, clean rooms and special production processes. This is comparable to other industries like electronics or photovoltaics that employ similar process steps.
Packaging and the associated backend process steps are important for production safety, especially in a highly volatile environment. They are also crucial for battery lifetime and performance. They have to be automated if possible and they have to be done in a way that minimises waste. There are many challenges, however, such as the need to keep a constant temperature or the requirement for workplace safety.
