The contradictory opposing sides of lithium battery development go hand in hand, and the loss of one side is no longer possible for the other side to exist. In the lithium battery, there are many similar to the zero-sum game of the two opposing sides, so that we can not help but praise the contradiction in the difficult choice of losing both sides.
1, the energy density of the battery and cell performance of the opposition
Capacity is the first property of the battery, while energy density is the primary issue that almost all batteries must consider when designing. When the design of energy density increases, the cell has to choose a thinner wish film, materials also need to be used in the limit of compaction and surface density. On the one hand, such an extreme design will make it more difficult for the cell to absorb the roll, thus affecting the cell's cycling performance; on the other hand, thinner diaphragm aluminum plastic film, higher energy density materials also means poorer safety performance. Energy density and cell performance, it can be said that any unit in the design of the battery had to encounter the problem; a unit is often when its energy density has a greater advantage, the cell cycle safety performance may have certain hidden dangers; when its cycle safety performance to do 100% error-free, energy density is often lower and make the product lacks a strong competitive edge.
2, the amount of liquid injection of lithium batteries and processing performance opposing
Single to the performance of the core, improve the amount of liquid injection is beneficial; but when more liquid injection, the processing performance of the core will be significantly reduced, the vacuum adsorption difficulties after liquid injection, hot and cold pressure and fixture baking when the core pressure burst, degassing after the soft core or even not sealed between the problem will ensue. Strictly speaking, the amount of liquid injection in the process must not allow the cores in the processing of batch abnormalities caused by excessive liquid injection, otherwise the amount of liquid injection will need to be reduced (if the result of the reduction is a drop in the amount of liquid retention and circulation NG, it means that the material should be replaced); of course, before confirming that the amount of liquid injection is problematic, optimization from the process point of view is also essential, such as adsorption difficulties can be increased adsorption tank capacity to improve efficiency, pressure explosion can not be adjusted to reduce the speed of the clamping plate down to reduce the proportion of pressure explosion, etc., when the process optimization has reached its limit or has reached its own short-term can not be further optimized, then reduce the amount of liquid injection it. When the fish and the bear's paw can not be both, the top leader said to that, that we need that good.
3、Production efficiency and product yields
For production, to improve production or efficiency is the goal sought in its bones, higher efficiency means shorter process cycle time and shorter time for processing in the production process, while the latter often results in lower product performance. Interestingly enough, many of the quality problems encountered in production can be improved by similar methods of "lowering production efficiency and increasing processing time"; for example, cracking during the coating process can be improved by lowering both temperature and speed, easy deformation in semi-automatic winding can be improved by winding at a slow speed followed by variable speed winding, and poor formation of SEI film can be improved by slowing down the winding speed and then speeding up the winding speed. The poor formation of SEI film can be improved by reducing the charging rate, and the softness of the cores after baking can be improved by extending the baking time and extending the resting time at room temperature before the cores are clamped. Statistically speaking, "time" here often acts as a "stabilization factor"; perceptually speaking, if an improvement can improve efficiency while increasing yield, then the method used before is not too level? When efficiency and yield conflict, the priority must be to ensure the yield, but also to understand the loss of efficiency of the production line in order to achieve the yield, the increase in personnel, equipment additions, production reduction, etc. Only think what people want, your improvement program will be accepted by people.
4、Lithium battery cathode gram capacity and expansion opposing
Silicon-based materials are a choice of future anode material direction, its ultra-high embedded group capacity as the biggest advantage; but at the same time the charge and discharge process is too large expansion is also an important limitation of its failure to promote. Graphite in the embedded lithium, lithium ions embedded in the middle of the graphite layer, its state is similar to the two layers of quilts put between a few small glass balls, deformation is bound to be small at the same time embedded lithium capacity is not too high. While the reaction between lithium and silicon, lithium directly inserted into the silicon silicon atoms, similar to the glass ball in the middle of a full flat and then insert more glass balls, although more lithium can be embedded, but at the same time occupy a larger volume is bound to. The apparently related "lithium insertion capacity" and "lithium insertion size" are actually determined by the mechanism of lithium insertion. In other words, when a material has a larger capacity, its charge and discharge deformation is often prone to greater, and its promotion is bound to be limited. Of course, excellent materials can certainly be researched, the expansion of the material can also be improved by way of coating or nano-treatment, and there is no inevitable result of high capacity deformation must be large (rather than "result", rather than say that this is a trend), with the progress of science and technology, the development of new materials will become more and more Important (it seems that one of the main reasons for China's engine NG is that the material is not up to scratch).
5, lithium battery cathode energy and safety
The higher the energy of the material, the more unsafe it will be. When the energy of a material is higher, it means that the amount of debonding after charging is greater, and the structural changes are also greater, so it is also more unstable; for example, after the full charge of the drill acid group, there will be more 4-valent drill present, which increases the oxidation of the cathode, as the cobalt acid bond skeleton of Co02-1 (cobalt acid root?) The structure of Co02-1 (cobaltate?), which is the backbone of the cobalt-acid bond, is destroyed, making the cathode material more susceptible to decomposition and reducing safety. However, when a material is low energy, the charge will also lose less bond, the material itself is better retained in the structure of the safety will be improved; iron phosphate bond after full charge, as the skeleton structure, accounting for a large proportion of the entire molecular phosphate is not destroyed, the molecular structure is not destroyed, its safety is naturally higher. With the negative gram play and expansion may seem to be related, but they are determined by the structure of the material, the positive gram play and safety may seem to be negatively related, but they are also determined by the structure of the material itself.
The materials, design, and process of battery are a unified whole, endlessly related to each other and derived from the most fundamental theoretical basis. In the design of battery cells, it is inevitable that there will be times when both sides of the contradiction reach the best point at the same time. It is absolutely impossible to find the best balance point or choose the direction that you are more concerned about as the priority reference orientation.
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