Everyone should be familiar with the battery cell, which is the energy storage component of the lithium-ion battery. The basic principle is to use chemical substances with different properties in the positive and negative electrodes of the battery core to carry out reversible redox reactions, thereby forming a charge and discharge process. Different materials have different potential differences, thus forming different voltages. The nominal voltage of currently commonly used ternary battery cells is 3.6V. No matter how large the volume of a single battery cell is, the battery cell will only increase the capacity without changing the voltage. Therefore, if you want to get a higher voltage, you need to connect the cells in series. Series connection increases voltage, parallel connection increases capacity.
According to different prclassification principles, battery cells can be classified into many categories, such as:
① Classify according to different positive and negative electrode materials
② According to appearance, classify according to different forms of packaging;
③Classify according to different uses.
The above classification methods are only the most common in our current use. In fact, different application scenarios can be arbitrarily classified according to needs. Even under any of the categories above, more detailed subcategories can be created.
Classification according to the materials of positive and negative electrodes
The ternary batteries, lithium iron phosphate batteries and lithium titanate batteries that everyone often talks about are actually classified according to materials positive and negative electrodes. of the battery core. The ternary battery cell refersence to the material of the positive electrode of the battery core composed of three elements. Specifically, there are slight differences between the domestic Sanyuan and the Panasonic Sanyuan used by Tesla. Domestic ternary, we call it nickel-cobalt-manganese (NCM) ternary, which means that the positive electrode material of the battery core is composed of three elements: nickel, cobalt and manganese, while the ternary of Panasonic is nickel-cobalt-aluminum (NCA) ternary. Under the classification of ternary batteries, there are hardware systems subdivided according to the different ratios of the three elements. Different ratios, battery cores have different performance. At present, the most mature and commonly used battery cell in China is 523. In addition, ternary batteries with high energy density and high nickel content (811, nickel accounts for 80%) have also been developed and aMass production was achieved.
The name of lithium iron phosphate (LFP) is the same as that of the ternary battery. Lithium iron phosphate refers to the material of the positive electrode of the battery. Lithium iron phosphate and ternary are both positive electrode materials, and their negative electrodes are usually graphite.
What should be noted here is that lithium titanate batteries are different from ternary batteries, and lithium iron phosphate is a negative electrode material, not a material positive electrode. The negative electrode material, lithium titanate, can be combined with the positive electrode material, lithium iron phosphate and ternary, to respectively form a battery cell, what we call a lithium battery. lithium titanate.
In addition to the above three types of battery cells, there are also a variety of matebattery base materials, such as lithium manganate and lithium cobalt oxide, but they are rarely used in the field of power batteries. Due to the energy density requirements of power batteries, ternary batteries have the highest share, followed by lithium iron phosphate, while lithium titanate has a small number of applications in buses and special stages. Below, let's compare the properties of each battery cell:
In comparison, the lifespan of lithium iron phosphate is longer than that of ternary battery cells, and it has advantages in terms of safety and cost. However, the energy density of ternary energy has an absoluteAdvantage.
As for the voltage platform, the voltage platform of ternary batteries is higher than that of other materials. The nominal voltage of ternary batteries is generally 3.6 V, while that of lithium iron phosphate is 3.2 V and that of lithium. titanate is about 2V.
Classification according to the shape of the packaging
As you often see, the 18650, square case, soft package, etc. which we often talk about are classified according to the shape of the packaging. Battery core. Generally, there are three types:
①cylindrical battery core;
②square shell battery cell;
③soft battery core.
Among them, cylindrical batteries have the highest degree of standardization. At present, 18650 batteries are widely used, and their surrounding supporting materials also have a high level of standardization. The cylindrical core housing of the battery is made of steel shell material, the entire bottom surface and sides are negative electrodes, and the upper surface is positive electrode.
The naming method for cylindr batteriesiques is generally five numbers: diameter size + height size + 0, like the 26650 battery core, which means that the cylindrical battery core is directly 26mm and 65mm in height. end means cylindrical shape.
The naming method of square battery cells is similar to that of cylindrical battery cells, but the square shape has six digits, and two digits are used to represent the thickness, width and height respectively .
The above only represents our common naming habits. If you need a standardized name, you can refer to the IEC61960 standard.
Rectangular batteries and soft-packaged batteries are less standardized and are usually customized in size depending on requirements. The shell material of square battery cells is usually aluminumm, that's why it is also called aluminum square shell battery cell. The soft-packaged battery core housing is made of a polymer material, which can of course also be called aluminum-plastic film.
Next, let's look at the differences between the three types of battery cells:
Cylindrical battery cells have a high degree of standardization, and the surrounding materials are also highly standardized. Their size is small, so they are grouped together. Very flexible and can be used in different spaces. Square case and soft batteries are usually larger in size and can be customized in size depending on space. Therefore, in actual use, cylindrical cells are most commonly used for small-scale or single-unit battery needs.
Classification according to usage scenarios
The last methodclassification is relatively simple, which consists of classifying according to use. Generally speaking, we usually divide them into electric batteries and digital batteries. Among them, power cells refer to cells used in power batteries, while digital cells refer to cells used in consumer electronic products, such as laptop power supplies, power banks for cell phones, etc.
The requirements for power batteries are more stringent, such as higher energy density and power density. In other words, the same volume and weight are needed to produce more power and electricity. In addition, there are stricter requirements for working environment and service life. Of course, security is also an important consideration.
Okay, I'll sharebattery cell information with you here. Next time, we will focus on explaining the lithium battery protection board information. If you have any questions, you can leave a message in. advance.
@电车 Battery Replacement Talk, specializes in sharing information and materials about electric vehicles, especially the replacement of electric vehicle batteries. At the same time, we also share with you the Battery theory and manufacturing information for two-wheeled vehicles, low-speed four-wheeled vehicles and electric vehicles. Interested readers can pay attention!
This article is from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.