The capacity is not enough, the unit price is lower, the cycle is better, and the safety is even higher. The batteries that are made may be unattractive. So how can we increase the energy density of the battery?
Raising the battery's energy density (capacity-type batteries only) is the top priority for designing batteries.
The capacity is not enough, the unit price is lower, the cycle is better, and the safety is even higher. The batteries that are made may be unattractive. So how can we increase the energy density of the battery? It can mainly be considered in several ways:
➀. Increase the performance of materials that contribute to battery capacity;
âž. Reduce the volume of material that does not contribute to battery capacity;
âž‚. Use more advanced production equipment;
➃.Improved manufacturing process conditions and stricter production monitoring;
âž„. Optimize the miscellaneous items that affect the capacity;
The following classification began to discuss separately:
â¶. To increase the performance of materials that contribute to battery capacity: This is the most direct method for increasing the capacity density for positive and negative active materials. The main directions include:
The use of grams to play a larger material: for example, the positive electrode of lithium-rich materials, high voltage ternary materials, high-voltage lithium cobalt oxide materials, binary materials, etc.; negative soft carbon hard carbon, silicon-tin compounds.
âž Use more positive and negative materials with higher densities.
âž‚ Use of adhesive and conductive materials: This can reduce the content of binders and conductive agents in the dressings, thus increasing the capacity of the unit mass of dressings; and reduce the amount of binders and conductive agents used. It can also improve the processing performance of the active material such as compaction.
➃ Use materials with smaller thickness rebound: Lithium-ion batteries will have a certain thickness rebound after cycling; design need to reserve the thickness of the rebound after the cycle; and when using materials with smaller thickness rebound (as currently seen Look, these materials are also good cycle performance materials at the same time), you can transfer the saved thickness to reserve the space to the design thickness of the cell, thus increase the design capacity of the cell.
âž„ Choosing a material system with better performance: A single “good cathode†or “good cathode†is paired with a “good electrolyte†and cannot guarantee a “good batteryâ€. The combination of poorly matched materials will not only reduce the cycle performance of the battery, but also affect the rate performance and even the positive and negative electrode performance. Similarly, when the material matching is better, the play, cycle, and expansion rate Such performance may be improved.
With the increasing maturity of lithium-ion battery material technology, the potential of common lithium cobalt oxide and graphite has almost reached its limit. If other mature systems can be produced in the future, the energy density of lithium-ion batteries will have a revolutionary impact!
â·. Reducing the volume of material that does not contribute to the battery capacity: This item is relatively complicated, mainly including the use of thinner aluminum film, the use of thinner battery separators, the use of thinner tabs, and the use of thinner copper foils. And aluminum foil, use thinner transparent adhesive tape and so on.
It can be seen that improvements in this area are basically attributed to “thinnessâ€. With a limited volume, the reduction in the volume of the aluminum plastic film, separator, etc., which does not directly contribute to the capacity means that the amount of the chemical substance that can provide the capacity is increased, thereby increasing the capacity of the cell.
However, when these materials are thinner, their mechanical strength and safety performance will be affected; on the other hand, the auxiliary material manufacturers need to reduce the volume without substantially reducing the performance of the materials. On the other hand, the battery manufacturers need to change the process, Made of parameters or even equipment (for example, thinner aluminum foil means higher stick pressure extension factor and increased probability of fragmentation during coating and stick pressure; thinner diaphragm has a higher risk of short-circuit rate; thinner aluminum foil The film is more prone to foot damage; thinner tabs can reduce the battery's rate performance, etc.).
Replacement of these thinner materials requires battery manufacturers to do a lot of certification. If the number of trial production is too small, statistical data cannot be accurately obtained. If too many problems occur, it will result in waste. Compared with improving the performance of active substances, reducing the content of non-active substances seems to have more ideas and the same is true in terms of success.
â¸. Use more advanced production equipment: advanced equipment is mainly to improve the consistency of the production, reduce production fluctuations, and then to achieve the maximum value without changing the mean value, and determine the quality of a batch of batteries, precisely It is the raised minimum here. Take the following two examples:
When the coater's coating tolerance is smaller, the minimum capacity/design capacity can be increased. If the customer has a requirement for the minimum capacity, it is equivalent to an increase in the minimum capacity when the design capacity is constant, that is to say, Improve the evaluation of the capacity of the battery to the customer; at the same time, the deviation of the positive and negative electrodes is reduced. After considering the factors such as the first-time efficiency and the capacity attenuation after the cycle, the excess of the designed negative electrode can be moderately reduced, so that the battery has more positive electrodes. Material is equivalent to having more capacity.
When the precision of the roller press is improved, the design compaction can be closer to the maximum compaction of the material due to the reduction of the error during the actual rolling, thereby increasing the design capacity and making the cell capacity; rolling the pole piece The more uniform thickness, which is equivalent to increase the consistency of the core thickness, and then can be selected in the design of smaller maxTHK-designTHK, thereby increasing the design capacity (cutting knife width, tape width, accuracy of the separator cabinet And so on, it will not repeat them).
â¹.Improved production conditions and stricter production monitoring. There is a lot of knowledge in production control, enumerating one or two:
➀ Reduce the turn-to-spin time after rolling to the winding: This will reduce the thickness rebound of the pole pieces and thus better control the cell thickness. If the cell thickness is significantly lower than the maximum thickness, the design thickness can be appropriately increased to improve the cell design capacity.
âž Stable compartmentalized room temperature: The temperature has a great influence on the capacity of the cell. The low temperature may cause the qualified cell of the capacity to be transferred to the secondary capacity and then to the secondary capacity to waste resources. The high temperature may increase the capacity. Poor batteries shipped as qualified products.
As with the principle of short board, the capacity of a batch of batteries is based on the lowest value of the shipped batteries, and the thickness of a batch of batteries is measured as the maximum thickness of the shipped batteries. People's operation in our country's labor-intensive industries, the impact of the quality of the product is particularly important. In production, if the operator and quality personnel can reduce the error of human operation as much as possible and reduce the fluctuation during manufacture, it is equivalent to increase the length of the shortest board in the barrel, thereby increasing the capacity of the battery and reducing the battery. thickness of.
âº. Optimize the miscellaneous items that affect the cell's capacity.
The fully charged core is disassembled and the negative body should be uniform and perfectly golden. However, when there are problems with human operations, materials, equipment, and even the design, various types of minor defects such as: the first coil of the core negative electrode, the separator, the separator is wrinkled, the lithium is deposited, and the density of the positive and negative tail films is uneven. Problems will arise.
From the perspective of capacity, lithium is likely to cause low capacity; if it is possible to eliminate similar situations, it is equivalent to increasing the capacity of the cell; if it is impossible to eliminate such situations, it needs to be more accurately predicted from the design. The probability and magnitude of the impact that may be generated, thereby avoiding some batteries from being scrapped due to problems that could have been predicted.
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