Increasing 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 also be unattended. So how can we increase the energy density of the battery? It can mainly be considered in several ways:

1. Increase the performance of materials that contribute to battery capacity;

2. Reduce the volume of material that does not contribute to battery capacity;

3. Use more advanced production equipment;

4. Improve the manufacturing process conditions and conduct more stringent production monitoring;

5. Optimize the miscellaneous items that affect the capacity;

The following classification began to discuss separately:

1. Increase the performance of materials that contribute to battery capacity:

Here, it is the most direct method for increasing the capacity density for positive and negative active materials. The main directions include:

1 Uses gram to play bigger material: For example positive pole lithium rich material, high voltage ternary material, high voltage lithium cobalt oxide material, binary material, etc.; negative pole soft carbon hard carbon, silicon tin base compound and so on.

2 Use more positive and negative materials with higher densities.

(3) The use of adhesive and conductive materials with better activity: This can reduce the content of binders and conductive agents in the dressings, thereby increasing the capacity of the unit mass dressings; and the use of binders and conductive agents can be reduced. It can also improve the processing performance of the active material such as compaction.

4 Use materials with smaller thickness rebound: After lithium-ion battery cycling, there will be a certain rebound in thickness; design needs to reserve the rebound thickness 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.

5 Choose the material system with better performance: a single “good cathode”, “good cathode” and “good electrolyte” are combined, and it cannot guarantee to make a “good battery”. 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!

2. Reduce the volume of material that does not contribute to battery capacity:

This item is relatively complicated, mainly including the use of thinner aluminum films, the use of thinner battery separators, the use of thinner tabs, the use of thinner copper foils and aluminum foils, and the use of thinner transparent adhesive tapes.

It can be seen that improvements in this area are basically attributed to “thinness”. 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.

3. The use of 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 average value, and determine the quality of a batch of batteries, precisely It is the raised minimum here. Take the following two examples:

1 When the coater's coating tolerance is smaller, the minimum capacity/design capacity can be increased. If the customer has the minimum capacity requirement, it is equivalent to increase 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 taking into account factors such as the first time efficiency and capacity attenuation after the cycle, the design negative electrode can be moderately reduced, and thus the battery has more positive electrodes. Material is equivalent to having more capacity.

2 When the accuracy 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 out 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).

4. Improve the manufacturing conditions and conduct more stringent production monitoring.

There is a lot of knowledge in production control, enumerating one or two:

1 reduce the rolling time after rolling to winding: This can reduce the thickness of the pole bounce, and thus better control the thickness of the battery. If the cell thickness is significantly lower than the maximum thickness, the design thickness can be appropriately increased to improve the cell design capacity.

2 Stable compartmental 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 to be a low capacity, thus wasting resources, and 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 fluctuations during manufacture, it is equivalent to increasing the length of the shortest board in the barrel, thereby increasing the capacity of the battery and reducing the battery. thickness of.

5. 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: first winding of the core negative electrode, lithium separation, lithium deposition at the diaphragm wrinkle, uneven density at the positive and negative tail films, and lithium deposition 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 not possible 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.