What's the difference between a polymer lithium battery and a power lithium battery?

Polymeric batteries are divided into ordinary discharge batteries and high-discharge batteries (power battery/avionics batteries). The diaphragm and copper sheet used in high magnification polymer batteries are not normal times. The batteries are thick.

Polymer batteries are generalizations of soft-coated lithium batteries, and some of the power lithium batteries are also polymer batteries. That is to say, the soft package power lithium battery is also a polymer battery.

At present, there are three main forms of lithium battery packaging, namely cylindrical, Square and soft package. Different packaging structures mean different characteristics. Each of them has its own advantages and disadvantages. Judging from the market development trend in recent years, the proportion of soft-pack batteries is increasing, and experts expect that the market share of soft-pack batteries in the future is expected to exceed 50 %.

Cylinder Battery: The production process is mature and the product yield is high

There are many models of cylindrical lithium batteries, such as 14650, 17490, 18650, 21700, and 26500. The production process of cylindrical lithium cells is mature, PACK is low in cost, the yield of battery products and the consistency of battery packs are high; Due to the large heat dissipation area of the battery pack, its heat dissipation performance is better than that of the square cell; The cylindrical battery is convenient for many kinds of configuration, and is suitable for the adequate layout of the space design of electric vehicles. However, cylindrical batteries are generally packaged in steel or aluminum shells, which are relatively heavy and relatively low in energy. At present, China, Japan, Korea, and the United States all have mature production companies, such as SANYO, SONY, LG, and Wanxiang A123.

With the further expansion of the electric vehicle market and the continuous improvement of the mileage requirements, the vehicle companies have put forward higher requirements for power batteries in terms of energy density, manufacturing costs, cycle life, and product additional attributes. Under the premise that no great breakthrough has been achieved in the field of raw materials, properly increasing the volume of cylindrical batteries to obtain more battery capacity has become an exploration direction. Currently, Tesla has started large-scale production of 21700 batteries and plans to use it on Tesla's Model 3. If tested on other Tesla models, it will replace all the previously used 1,8650 batteries. Tesla's approach may lead to a "21700 wave" around the world.

Square Hard Shell Battery: Too many models and difficult to unify

The square hard shell battery shell is mostly aluminum alloy, stainless steel, and other materials. The internal winding or folding process is used. The protective effect on the electric core is better than that of the aluminum plastic membrane battery (ie, the soft package battery). The safety of the electric core is relatively cylindrical. The battery has also greatly improved.

Lithium battery aluminum shell was developed on the basis of the steel shell. Compared with a steel shell, lightweight and safety and the resulting performance advantages make aluminum shell become the mainstream of lithium battery shell. Lithium battery aluminum shell is still developing in the direction of high hardness and lightweight technology, which will provide the market with more advanced lithium battery products. At present, the companies that produce square hard shell batteries include Guoxuan Gaoke, Samsung SDI, Lishen, and Ningde Times.

Since square lithium batteries can be customized according to the size of the product, there are thousands of models on the market, and because there are too many models, the process is difficult to unify. There is no problem with the use of square batteries in ordinary electronic products, but for industrial equipment products that require more than one series and parallel, it is best to use standardized cylindrical lithium batteries. This production process is guaranteed and it is easier to find replaceable batteries in the future.

Introduction to 18650 Lithium Battery

The 18650 is the originator of the lithium-ion battery -- a standard lithium-ion battery model set by the Japanese SONY company in order to save costs, of which 18 represents a diameter of 18mm, 65 represents a length of 65mm, and 0 represents a cylindrical battery.

Common 18650 batteries are divided into lithium ion batteries and lithium iron phosphate batteries. The lithium-ion battery voltage is a nominal voltage of 3.7 V, the charging cut-off voltage is 4.2 V, the lithium iron phosphate battery has a nominal voltage of 3.2 V, the charging cut-off voltage is 3.6 V, the capacity is usually 1200 mAh-3350 mAh, and the common capacity is 2200mAh-2600mAh.

18650 lithium battery use:

The 18650 battery life theory is 1000 cycles. Due to the large capacity of the unit density, most of it is used in notebook computer batteries. In addition, the stability performance of the 18650 in the work is very good, and it is widely used in major electronic fields: it is commonly used in high-end strong light handsets, portable power supplies, wireless data transmitters, Electric heating clothing, shoes, portable instrument, portable lighting equipment, portable printers, industrial equipment, medical equipment and so on.

18650 Lithium batteries and soft-pack batteries who are more suitable for electric cars

18650 lithium battery advantages:

1, the capacity of a large 18650 lithium cell is generally between 1200mAh and 36000mah, while the general cell capacity is only about 800mAh. If combined into a 18650 lithium battery pack, the 18650 lithium battery pack can easily break through 5000 mAh.

2. Long life 18650 Lithium batteries have a long service life, and their normal service life can reach more than 500 times, which is more than twice that of ordinary batteries.

3, high safety performance 18650 lithium battery safety performance is high, do not explode, do not burn; Non-toxic, non-polluting, certified by the RoHS trademark; All kinds of safety properties are formed at one time, and the number of cycles is greater than 500 times; The performance of high-temperature resistance is good, and the discharge efficiency reaches 100 % under 65 degrees. In order to prevent the short-circuit of the battery, the positive and negative poles of the 18650 lithium battery are separated. So the possibility of it being short-circuited has been minimized. You can install a protective plate to avoid overcharging the battery, which can also extend the service life of the battery.

4, voltage height 1,8650 lithium battery voltage is generally 3.6 V, 3.8 V and 4.2 V, much higher than the nickel cadmium and nickel hydride battery 1.2 V.

5, no memory effect before charging will not have to empty the remaining power, easy to use.

6, the internal resistance is small: the internal resistance of the polymer core is smaller than that of the general liquid core, the internal resistance of the domestic polymer core can even be below 35mΩ, greatly reducing the battery's self-consumption, and extending the mobile phone's standby time. It is possible to achieve an international level. This polymer lithium, which supports large discharge currents, is an ideal choice for remote control models and is the most promising alternative to nickel-metal hydride batteries.

7, can be combined in series or in parallel into a 18650 lithium battery pack.

8, use a wide range of laptops, walkie-talkies, portable DVDs, instrumentation, audio equipment, avionics, toys, cameras, digital cameras, and other electronic equipment.

18650 Lithium batteries and soft-pack batteries who are more suitable for electric cars

18650 lithium battery disadvantages:

The biggest drawback of the 18650 lithium battery is that its size has been fixed, and it is not well positioned when it is installed in some notebooks or some products. Of course, this disadvantage can also be said to be an advantage. This is a disadvantage compared to the customizable and convertible sizes of lithium batteries such as other polymer lithium batteries. And it has become an advantage over some products that specify battery specifications.

The 18650 lithium battery is prone to short circuit or explosion, which is also relative to the polymer lithium battery. If the battery is relatively general, this disadvantage is not so obvious.

The 18650 lithium battery production requires a protective line to prevent the battery from being overcharged and causing discharge. Of course, this is necessary for lithium batteries, which is also a common disadvantage of lithium batteries, because the materials used in lithium batteries are basically lithium cobalt acid materials, while lithium batteries of lithium cobalt acid materials can not discharge large currents. Poor safety.

The production conditions of the 18650 lithium battery are high. Compared with the general battery production, the 18650 lithium battery has high requirements for the production conditions, which undoubtedly increases the production costs.

Introduction to Lithium Battery in Soft Packages

Lithium batteries are just liquid lithium-ion batteries coated with a polymer shell. In the structure of aluminum plastic film packaging, in the event of safety hazards, the flexible battery will only crack the gas.

The advantages of soft pack batteries:

1. Good Safety Performance

Soft pack batteries do not explode like steel shell aluminum shell cores.

2. Lightweight

The weight of the flexible battery is 40 % lighter than that of the same capacity lithium steel shell and 20 % lighter than the aluminum shell battery.

3. Large capacity

Soft pack batteries have a capacity of 10 to 15 % higher than steel shell batteries of the same size and 5 to 10 % higher than aluminum shell batteries.

4. Small internal resistance

The internal resistance of the soft-pack battery is smaller than that of the lithium battery. At present, the internal resistance of the domestic soft-pack battery core can be below 35mΩ, which greatly reduces the battery's self-consumption.

5. Flexible design

The shape of the soft pack battery can be customized according to the customer's needs and a new type of core can be developed.

18650 Lithium batteries and soft-pack batteries who are more suitable for electric cars

Disadvantages of soft pack batteries:

The existing soft pack battery core models are few and can not meet the market demand;

Developing new models is expensive.

18650 Lithium batteries and soft-pack batteries who are more suitable for electric cars

Third, 18650 lithium batteries and soft-pack batteries who are more suitable for electric cars

What makes the world's most famous electric car brand different about power batteries? In the field of automotive power battery applications, where are the advantages and disadvantages of the 18650 lithium battery and the soft pack battery?

The difference in the form of electrolytes is the key.

As the two mainstream power batteries on the market, the 18650 battery and the Lithium-Polymer soft-pack battery are distinguished by the shell packaging material. The 18650 battery is generally a steel shell package (18 means a diameter of 18mm, 65 means a length of 65mm, and 0 means a cylindrical battery). The structure of the internal electrode sheet and the diaphragm is coiled. Lithium polymer soft pack batteries are packaged with aluminum-plastic film, and the internal electrode sheet and diaphragm are stacked (layer by layer).

Although the shape and internal structure are different, the principles of the two batteries are basically the same. Both types of batteries have positive poles, negative poles, and electrolytes. Positive materials are generally lithium cobalt phosphate, lithium nickel cobalt manganese acid (ternary material), lithium ferric phosphate or lithium manganese acid, etc.. Negative materials are generally graphite, and electrolytes are Lithium hexafluorophosphate solution.

The main difference between the two is that one of the internal materials of the battery, the electrolyte, has a different form: the electrolyte inside the lithium polymer soft-pack battery uses a polymer, which is generally a gel or solid state, while the electrolyte inside the 18650 battery is generally a liquid.

18650 Lithium batteries and soft-pack batteries who are more suitable for electric cars

Each has its own advantages and disadvantages.

18650 lithium batteries and Lithium-Polymer soft-pack batteries have their own advantages and disadvantages. At present, the 18650 battery production has a high degree of automation, the consistency and safety of the battery have reached a high level, and the small size and light weight of the battery itself make it unique in the modularization and standardization of system development. Many people think that using the 18650 battery as the source of power for new energy electric vehicles is the best choice at this stage.

However, the 18650 battery also has the inevitable disadvantage that the monomer capacity is low (generally around 2 ~ 4 Ah). This makes the number of batteries required for the 18650 battery in application very large, and the battery management system that maintains the core consistency and heat dissipation of the battery is also more complicated.

Compared with the 18650 battery, the lithium polymer soft-pack battery has a higher monomer capacity and has the advantages of thinning, arbitrary area, an arbitrary shape (ultra-thin batteries such as 0.33 mm and 0.50 mm can be produced). Its main disadvantages are poor consistency and poor mechanical strength. Based on the characteristics of Lithium-Polymer soft-pack batteries, Lithium-Polymer soft-pack batteries are increasingly used in mobile phones, laptops, and mobile power sources. However, due to the poor conductivity of colloidal (or solid) electrolytes and the large internal resistance, Lithium-Polymer soft-pack batteries are rarely used in electric vehicles.

Soft-pack batteries aren't all lithium polymer batteries.

Since Lithium-Polymer soft-pack batteries are rarely used in electric vehicles, what type of battery are Nissan's cascading soft-pack batteries?

In fact, although Lithium-Polymer soft-pack batteries are generally referred to as soft-pack batteries because soft-pack batteries can also use liquid electrolytes, soft-pack batteries are not all lithium-polymer batteries. Nissan leaf batteries are soft-pack batteries that use liquid electrolytes.

Whether it is a lithium polymer soft-pack battery or a soft-pack battery whose internal material is a liquid electrolyte, soft-pack batteries are generally packaged in aluminum plastic membranes. The thickness of the aluminum plastic film is thin, and the mechanical strength is poor. Under extreme circumstances such as car collisions, aluminum plastic film is easily damaged and causes accidents. This is the main defect of the use of soft-pack batteries in new energy vehicles.

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