1s lipo battery design N/P ratio

1s lipo battery cell design table is one of the necessary tools for engineers who are developing materials for cell product development. The format of the design table is often different for each company, and even there are many kinds of design tables in a company.

The design table understood by CNHL is composed of three equations: the capacity equation (this article about the capacity of lipo battery has a detailed introduction, and the required partners can Click to read: The reason for the capacity of 6s lithium battery is a formula to understand!), volume equation, N/P ratio equation. Where capacity and volume are defined by the customer or by the process. The 1s lipo battery N/P ratio equation is explained as follows:

1.1s lipo battery N/P ratio definition

N/P ratio (Negative/Positive) is in the same stage and under the same conditions, the negative capacity of the opposite 1s lipo battery exceeds the capacity of the positive electrode. In fact, there is another way of saying it is called CB (cell Balance).
1s lipo batteryN/P calculation formula:
N/P = gram capacity of negative electrode active material × negative electrode surface density × negative electrode active material content ratio ÷ (positive electrode active material gram capacity × positive electrode surface density × positive electrode active material content ratio).

2.1s lipo battery charge and discharge N/P ratio

The same stage: 1s lipo battery charging and discharging has two stages, corresponding to different gram capacities, one is the first charging stage, and the other is the discharging stage, corresponding to the (first) charge N/P ratio and discharge N/P ratio respectively.
Regarding the discharge of lipo battery, the following article introduces the knowledge of self-discharge of lipo battery in detail. Interested partners can click to read:
lipo battery 3s self-discharge dry goods!
We know that the 1s lipo battery material has the first effect, which is the first (Coulomb) efficiency, that is, the first charge-discharge capacity ratio of the 1s lipo battery.

During the first charging process of the 1s lipo battery, the SEI film is formed on the surface of the material, the defect position of the material is reacted, the impurities in the material are also reacted, etc., resulting in the first charge capacity > the first discharge capacity > the discharge capacity after aging.
Although after aging and subsequent charge-discharge cycles, the discharge capacity of the 1s lipo battery still decays, but a large number of reactions have been completed in the early stage.
There are differences in the gram capacity of the two stages, one is the gram capacity of the first charge, and the other is the gram capacity after the first effect. Mixing them will cause the design of the 1s lipo battery to fail.
Same condition: The same condition is also relevant for gram capacity calculation. This condition refers to the same test conditions, such as temperature, magnification, voltage range, etc.

If the gram capacity test conditions of the positive and negative electrodes of the 1s lipo battery are different, using the same formula will also cause the design to fail.
Directly opposite: We need to calculate the area density, which is the meaning of being right. But what if the shape of the pole piece of the 1s lipo battery is bent and deformed? That is, when the outer ring shrinks and the inner ring stretches, we use the curvature to correct the value of the surface density, which is why the cylindrical 1s lipo battery has yin and yang surfaces during the coating process.

3. Factors should be considered when designing the N/P ratio of 1s lipo battery

First, the first effect of 1s lipo battery:

The first effect of 1s lipo battery is to consider all reactive substances, including conductive agents, adhesives, current collectors, diaphragms, and electrolytes. But the gram capacity data we get from 1s lipo battery material suppliers often only consider the half-electric gram capacity of the active material, which is why there is a difference between the actual full battery gram capacity and the design gram capacity.

Second, 1s lipo battery assembly process:

There is a difference in the design of the N/P ratio between the cylindrical battery and the square battery, which is mainly caused by the tightness of the contact between the positive and negative plates. We also consider the combination of powder and current collector as assembly. The direct contact between powder and current collector and the contact between powders are also one of the factors that affect the gram capacity and thus the N/P ratio of 1s lipo battery.

Third, 1s lipo battery formation process:

Different formation processes also have an impact on the N/P ratio. The formation process also affects the first effect by affecting the gram capacity. Therefore, when we design the N/P ratio of 1s lipo battery, the formation process should also be discussed. The impact of the specific formation process will be explained in subsequent articles.
performance factor

Fourth, 1s lipo battery cycle life:

Cycle life is one of the most important indicators to measure the performance of 1s lipo battery. If the positive electrode decays quickly, the N/P ratio is lower than the design, and the positive electrode is in a shallow charge and discharge state. On the contrary, if the negative electrode decays quickly, the N/P ratio is higher, so that the negative electrode of the 1s lipo battery is in a shallow charge and discharge state. This content will be discussed in detail in (below) of this article.

Fifth, 1s lipo battery safety:

Safety is a more important indicator than 1s lipo battery cycle. Not only does it have an impact on the safety performance of the finished product, but some pre-charged cells have lithium precipitation and heat generation. We need to review whether there are design problems.
Well, the above is the whole content of the 1s lipo battery N/P ratio that CNHL brought to you today. I believe that after reading the whole text, everyone's definition of 1s lipo battery N/P ratio, charge and discharge N/P ratio and design of 1s lipo batteryN/P The factors that should be considered at the time have been understood, and more lipo battery information can be obtained by clicking below:
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