Selection of battery materials and processing flow -Lithium - Ion Battery Equipment
The mining and production of lithium-ion battery raw material resources mainly include lithium-ion resources, cobalt resources and graphite.
Energy density, cost, safety, thermal stability, and cycle life are the five key indicators of power lithium-ion batteries. Ternary materials, potassium manganate and lithium iron phosphate have no absolute advantages in these five aspects. Lead to the difference in the route of power lithium-ion battery electrode materials.
The design of a battery starts with the selection of materials, and the appropriate materials should be selected according to the target requirements, such as energy density, rate characteristics, cycle life and safety. In terms of positive electrode material selection, we can choose LiFePO4 with olivine structure, which is more suitable for buses that do not require high energy density. In addition, there are high-capacity layered materials, such as NCM and NCM, which are more It is suitable for application in pure electric vehicles, and LiMN2O4 with spinel structure is more suitable for application in hybrid vehicles.(Lithium - Ion Battery Equipment)
In terms of negative electrode materials, graphite has always been the best choice for lithium-ion battery negative electrode materials. In fact, if only energy density is considered, metal tin is more suitable as a negative electrode material.
In order to improve the conductivity of the positive and negative electrodes, a small amount of conductive agent is usually added to it. At present, the most common conductive agents are carbon black materials, carbon fiber materials, and carbon nanotubes and graphene materials that have emerged in recent years. .
In addition, in order to adhere the electrode to the surface of the current collector, 1-4% binder is added. The current binders are mainly divided into two categories: one is oil-based binders, and the other is water-based binders. binder.
The four components of the battery are very critical: the positive electrode (discharged as the cathode), the negative electrode (discharged as the anode), the electrolyte, and the diaphragm. The positive and negative poles are where chemical reactions occur, and their importance is understandable. But what are electrolytes for? Doing work still accounts for a lot of weight.
Inside the battery, metal lithium ions lose electrons at the negative electrode and are oxidized to become lithium, which is transferred to the positive electrode through the electrolyte; the positive electrode material gets electrons and is reduced, and is neutralized by the lithium coming from the positive electrode. The ideal use of electrolytes is to transport, and only transport, lithium. Outside the battery, electrons are transferred from the negative electrode to the positive electrode through an external circuit, and work is done in between. Ideally, the electrolyte should be a good lithium carrier, but never a good electron carrier. Therefore, in the absence of an external circuit, electrons cannot transfer from the negative electrode to the positive electrode inside the battery; only when there is an external circuit, the electron transfer can take place.
Processing of single battery
The first step, the processing of single electrode
Mixing: Mix electrode active materials, binders, solvents, etc., and fully stir and disperse to form a slurry.
Coating: Evenly coat the prepared slurry on the current collector (aluminum foil or copper foil, etc.) with a specified thickness.
Baking: High temperature baking drying treatment.
Mixing and baking are related. The purpose of baking is to better fix the mixed slurry on the aluminum foil or copper foil. The baking process is a high energy-consuming link. If this link can be improved, the positive current of the lithium-ion battery can be reduced. Negative electrode processing cost.
The homogenization of lithium-ion batteries is a key link in the processing of lithium-ion batteries. The important part of the homogenization process is to mix active materials, binders, conductive agents and other components into a uniform suspension. Usually, we will first disperse the binder into a Glue, and then there are some processes that first disperse the conductive agent with the glue to form a conductive glue, and then mix it with the active material.
Some processes will mix the conductive agent and the binder together with the glue. The key to the homogenization is how to disperse the components in the slurry evenly. In order to achieve this goal, the homogenization process must be optimized. At present, the most important The homogenization process is mainly divided into dry homogenization and wet homogenization. At present, with the gradual popularization of nano-materials, lithium-ion battery manufacturers have also begun to use high-speed dispersion equipment, and use high-speed shearing to make the slurry more dispersed. In addition, many material manufacturers have developed a large number of additives to improve the dispersion of slurry.
The second step, the processing of the single battery
After completing the above-mentioned electrode drying process, we enter the next step of lithium-ion battery processing, the processing of single cells.
Pressing: Rolling is to roll and press the coated positive and negative materials to make them more compact and adhere to aluminum foil or copper foil.
Cutting: Slitting is to cut the rolled pole piece into strips according to the process standard.
In order to prevent the dried electrodes from absorbing water again, the entire cell processing process must be carried out in a drying room.
There are three main types of processing technology for square power lithium-ion battery cells, one is the winding process, which is generally used in the processing of cylindrical batteries, and is currently also used in the processing of square batteries. The important advantage is that the processing efficiency is high, and continuous processing can be realized. The disadvantage is also obvious. Because the bending angle at the edge of the cell is relatively large, it is easy to break the electrode and cause defects, especially in the case of thick electrodes. more serious;
The second is the lamination process. The lamination process is an ideal process. The positive and negative pole pieces will first be punched to obtain a specific shape of the pole piece, and then the positive or negative pole piece is selected to make a packaging bag with a diaphragm. The advantage of this process is that it will not cause deformation of the pole piece, and thicker electrodes can be used. However, since the lamination process is a discontinuous process, the lamination process The processing efficiency is relatively low, and there are relatively few manufacturers using this process;
The third is the Z-type lamination process. This process uses a continuous diaphragm and places the punched positive and negative electrodes in the middle of the diaphragm. This process not only retains the advantages of the lamination process, but also accelerates the process. The processing process has improved the processing efficiency, and there are more applications at present.
The processed battery core must first be welded with tabs. The main way of welding the tabs is to use ultrasonic welding technology. The battery core processed by the winding process is limited by the structure of the battery core. A single battery core cannot be made very thick, so usually the 2-4 battery cells are connected in parallel to weld the tabs. There is no restriction on the structure of the battery processed by the stacking process, so a single battery cell is generally welded to the tabs. The next step is the shelling process. After the battery core with the welded tabs is wrapped with a protective film, it is loaded into the battery shell. Ultrasonic welding, riveting and other processes are connected together, and then the upper cover and the outer shell of the battery are welded together by laser welding.
After the welding is completed, leak detection is usually performed, and batteries with unqualified leak rates are removed. Common leak detection methods include direct pressure, double pressure, and differential pressure. Good sealing is to ensure the performance of lithium-ion batteries. The key to long-term stability and reliability, so battery leak detection is also an essential link in the processing of square power lithium-ion batteries.
The battery that has passed the leak detection and screening is next to the very important liquid injection process. Since the electrolyte of lithium-ion batteries is very sensitive to moisture, the liquid injection process must be carried out inside the drying room. In order to improve the wetting effect of the electrolyte, it is usually necessary to Perform vacuum injection.
The battery fully infiltrated by the electrolyte then enters the formation process. The main purpose of the formation is to activate the battery by charging and discharging the battery with a small current.
In addition, due to the problem of processing gas usually occurs during the decomposition process of the electrolyte, the gas may accumulate in the battery cell, resulting in insufficient electrolyte infiltration. Therefore, some manufacturers will discharge the gas produced during the formation process Arrange battery sealing after formation.
After formation, the battery needs to be aged. The so-called aging is to put the fully charged battery at a certain temperature. During the storage process, due to some side reactions inside the lithium-ion battery, the external voltage and internal resistance of the battery will decrease. Changes, by monitoring the voltage, internal resistance and capacity of the battery pack, it is possible to eliminate those batteries with unqualified self-discharge and internal resistance, so as to improve the consistency of the single battery, and the aging result is also the result of subsequent batteries. An important reference for package matching. In order to speed up battery aging and improve processing efficiency, manufacturers usually perform aging at high temperatures (50-60°C) to shorten battery aging time.
Energy density, cost, safety, thermal stability, and cycle life are the five key indicators of power lithium-ion batteries. Ternary materials, potassium manganate and lithium iron phosphate have no absolute advantages in these five aspects. Lead to the difference in the route of power lithium-ion battery electrode materials.
The design of a battery starts with the selection of materials, and the appropriate materials should be selected according to the target requirements, such as energy density, rate characteristics, cycle life and safety. In terms of positive electrode material selection, we can choose LiFePO4 with olivine structure, which is more suitable for buses that do not require high energy density. In addition, there are high-capacity layered materials, such as NCM and NCM, which are more It is suitable for application in pure electric vehicles, and LiMN2O4 with spinel structure is more suitable for application in hybrid vehicles.(Lithium - Ion Battery Equipment)
In terms of negative electrode materials, graphite has always been the best choice for lithium-ion battery negative electrode materials. In fact, if only energy density is considered, metal tin is more suitable as a negative electrode material.
In order to improve the conductivity of the positive and negative electrodes, a small amount of conductive agent is usually added to it. At present, the most common conductive agents are carbon black materials, carbon fiber materials, and carbon nanotubes and graphene materials that have emerged in recent years. .
In addition, in order to adhere the electrode to the surface of the current collector, 1-4% binder is added. The current binders are mainly divided into two categories: one is oil-based binders, and the other is water-based binders. binder.
The four components of the battery are very critical: the positive electrode (discharged as the cathode), the negative electrode (discharged as the anode), the electrolyte, and the diaphragm. The positive and negative poles are where chemical reactions occur, and their importance is understandable. But what are electrolytes for? Doing work still accounts for a lot of weight.
Inside the battery, metal lithium ions lose electrons at the negative electrode and are oxidized to become lithium, which is transferred to the positive electrode through the electrolyte; the positive electrode material gets electrons and is reduced, and is neutralized by the lithium coming from the positive electrode. The ideal use of electrolytes is to transport, and only transport, lithium. Outside the battery, electrons are transferred from the negative electrode to the positive electrode through an external circuit, and work is done in between. Ideally, the electrolyte should be a good lithium carrier, but never a good electron carrier. Therefore, in the absence of an external circuit, electrons cannot transfer from the negative electrode to the positive electrode inside the battery; only when there is an external circuit, the electron transfer can take place.
Processing of single battery
The first step, the processing of single electrode
Mixing: Mix electrode active materials, binders, solvents, etc., and fully stir and disperse to form a slurry.
Coating: Evenly coat the prepared slurry on the current collector (aluminum foil or copper foil, etc.) with a specified thickness.
Baking: High temperature baking drying treatment.
Mixing and baking are related. The purpose of baking is to better fix the mixed slurry on the aluminum foil or copper foil. The baking process is a high energy-consuming link. If this link can be improved, the positive current of the lithium-ion battery can be reduced. Negative electrode processing cost.
The homogenization of lithium-ion batteries is a key link in the processing of lithium-ion batteries. The important part of the homogenization process is to mix active materials, binders, conductive agents and other components into a uniform suspension. Usually, we will first disperse the binder into a Glue, and then there are some processes that first disperse the conductive agent with the glue to form a conductive glue, and then mix it with the active material.
Some processes will mix the conductive agent and the binder together with the glue. The key to the homogenization is how to disperse the components in the slurry evenly. In order to achieve this goal, the homogenization process must be optimized. At present, the most important The homogenization process is mainly divided into dry homogenization and wet homogenization. At present, with the gradual popularization of nano-materials, lithium-ion battery manufacturers have also begun to use high-speed dispersion equipment, and use high-speed shearing to make the slurry more dispersed. In addition, many material manufacturers have developed a large number of additives to improve the dispersion of slurry.
The second step, the processing of the single battery
After completing the above-mentioned electrode drying process, we enter the next step of lithium-ion battery processing, the processing of single cells.
Pressing: Rolling is to roll and press the coated positive and negative materials to make them more compact and adhere to aluminum foil or copper foil.
Cutting: Slitting is to cut the rolled pole piece into strips according to the process standard.
In order to prevent the dried electrodes from absorbing water again, the entire cell processing process must be carried out in a drying room.
There are three main types of processing technology for square power lithium-ion battery cells, one is the winding process, which is generally used in the processing of cylindrical batteries, and is currently also used in the processing of square batteries. The important advantage is that the processing efficiency is high, and continuous processing can be realized. The disadvantage is also obvious. Because the bending angle at the edge of the cell is relatively large, it is easy to break the electrode and cause defects, especially in the case of thick electrodes. more serious;
The second is the lamination process. The lamination process is an ideal process. The positive and negative pole pieces will first be punched to obtain a specific shape of the pole piece, and then the positive or negative pole piece is selected to make a packaging bag with a diaphragm. The advantage of this process is that it will not cause deformation of the pole piece, and thicker electrodes can be used. However, since the lamination process is a discontinuous process, the lamination process The processing efficiency is relatively low, and there are relatively few manufacturers using this process;
The third is the Z-type lamination process. This process uses a continuous diaphragm and places the punched positive and negative electrodes in the middle of the diaphragm. This process not only retains the advantages of the lamination process, but also accelerates the process. The processing process has improved the processing efficiency, and there are more applications at present.
The processed battery core must first be welded with tabs. The main way of welding the tabs is to use ultrasonic welding technology. The battery core processed by the winding process is limited by the structure of the battery core. A single battery core cannot be made very thick, so usually the 2-4 battery cells are connected in parallel to weld the tabs. There is no restriction on the structure of the battery processed by the stacking process, so a single battery cell is generally welded to the tabs. The next step is the shelling process. After the battery core with the welded tabs is wrapped with a protective film, it is loaded into the battery shell. Ultrasonic welding, riveting and other processes are connected together, and then the upper cover and the outer shell of the battery are welded together by laser welding.
After the welding is completed, leak detection is usually performed, and batteries with unqualified leak rates are removed. Common leak detection methods include direct pressure, double pressure, and differential pressure. Good sealing is to ensure the performance of lithium-ion batteries. The key to long-term stability and reliability, so battery leak detection is also an essential link in the processing of square power lithium-ion batteries.
The battery that has passed the leak detection and screening is next to the very important liquid injection process. Since the electrolyte of lithium-ion batteries is very sensitive to moisture, the liquid injection process must be carried out inside the drying room. In order to improve the wetting effect of the electrolyte, it is usually necessary to Perform vacuum injection.
The battery fully infiltrated by the electrolyte then enters the formation process. The main purpose of the formation is to activate the battery by charging and discharging the battery with a small current.
In addition, due to the problem of processing gas usually occurs during the decomposition process of the electrolyte, the gas may accumulate in the battery cell, resulting in insufficient electrolyte infiltration. Therefore, some manufacturers will discharge the gas produced during the formation process Arrange battery sealing after formation.
After formation, the battery needs to be aged. The so-called aging is to put the fully charged battery at a certain temperature. During the storage process, due to some side reactions inside the lithium-ion battery, the external voltage and internal resistance of the battery will decrease. Changes, by monitoring the voltage, internal resistance and capacity of the battery pack, it is possible to eliminate those batteries with unqualified self-discharge and internal resistance, so as to improve the consistency of the single battery, and the aging result is also the result of subsequent batteries. An important reference for package matching. In order to speed up battery aging and improve processing efficiency, manufacturers usually perform aging at high temperatures (50-60°C) to shorten battery aging time.
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