Types of portable power station battery and technical routes of companies

Portable power station battery includes cylindrical battery and pouch cell battery, cylindrical battery includes 18650 cylindrical battery and 21700 cylindrical battery.

Whether it is a hard-shell battery or a pouch cell battery, the internal structure (cathode, anode, separator, electrolyte) is not much different, the main difference is the battery shell. Pouch cell battery uses aluminum-plastic composite film as the shell material, while square and cylindrical batteries use metal material as the shell, also called hard-shell battery.

From the viewpoint of enterprise technology line, Hello tech, as the industry leader, mainly uses ternary materials, Ecoflow also mainly uses ternary materials, 3600Wh products use lithium iron phosphate, Goal Zero’s below 400Wh products use lead-acid batteries, above 400Wh use ternary lithium batteries, Pylon and Poweoak’s products use lithium iron phosphate.

Cylindrical lithium battery

Cylindrical lithium battery is a round lithium battery, this portable power station battery mainly consists of cathode, anode, separator, collector of cathode and anode, valve, overcurrent protection equipment, insulation parts and shell together. In the early stage, the shell material is more steel shell, and at this stage, aluminum shell is dominant.

Cylindrical lithium battery has a unified standard, so it can be manufactured and processed in large quantities, and the maturity and perfection of the battery manufacturer’s technology can make the production speed of cylindrical lithium battery higher; at the same time, it is more widely used, and its technology is more mature.

This portable power station battery can be divided into lithium iron phosphate battery, lithium cobalt acid battery, lithium manganese acid battery, cobalt-manganese hybrid battery and ternary lithium battery according to the filler material. According to the shell type can be steel shell lithium battery and polymer shell lithium battery. Different material system of the battery has different advantages.

Cylindrical lithium batteries usually use five digits to indicate the model number, starting with the number on the left, the first and second digits refer to the battery diameter, the third digit refers to the battery height, and the fifth digit refers to the circle. There are many models of cylindrical lithium batteries, the more common are 10400, 14500, 16340, 18650, 21700, 26650.

18650 battery

This portable power station battery is a standard lithium battery model developed by the Japanese company SONY for better cost savings, and the 18650 battery that we often refer to is actually a portable power station battery named after the size of the battery.

The common 18650 battery is also divided into lithium-ion batteries and lithium iron phosphate batteries, 18650 in the 18 refers to the diameter of the lithium-ion battery is 18mm, 65 indicates the length value of 65mm, 0 indicates that it is a cylindrical battery. The capacity is 31.5ah and the voltage is 3.6v, which is a very cost-effective battery.

The main advantages of 18650 batteries are:

Light weight, easy to carry and install.

Good discharge performance, which can be discharged continuously for more than 500 times under the rated capacity.

Low self-discharge polarization temperature, no effect on heat-sensitive components.

High cycle life and good reliability.

Disadvantages are:

Higher price.

Not accepted by the majority of users due to its large size, bulky and unattractive appearance.

Cylindrical 18650 batteries currently sold in the market are cylindrical aluminum case (1861-lf), cylindrical copper case (1861-c), and cylindrical iron case (1861-t). Among them, the most commonly used is the cylindrical aluminum case, 1861-hf and 1862-gn two models are more frequently used.

1865-hf type cylindrical aluminum shell lithium battery uses aluminum alloy material to make the outer box and inner box, 1862gn uses galvanized steel plate to make the outer box and inner box, and 1866gp uses stainless steel plate as the combination of outer box and inner box to design and manufacture.

21700 battery

The 21700 battery is a lithium battery with a diameter of 21 mm and a height of 70 mm. Due to its increased size and space utilization, the energy density of the battery unit and system is then increased, and its volumetric energy density is much higher than that of 18650 batteries.

Compared to 18650 batteries, the energy density of the whole pack composed of 2170 cells can be further improved, and the increased size allows the 21700 battery to add more lugs and charge faster. Of course with the same capacity pack, the 21700 battery can use fewer cells and the BMS control and protection algorithm is a bit simpler.

At present, the biggest drawback of 21700 battery is in the energy density, and the square battery and 4680 battery have a slight gap, and the slight increase in volume and size only solves part of the shortcomings of 18650 battery, and does not make it reach the final perfect state.

At present, the more popular 21700 batteries on sale are two, respectively 4200mAh (21700 lithium battery) and 3750mAh (21700 lithium battery). Coming soon is a larger capacity 5000mAh (21700 Li-ion battery).

Pouch cell battery

This portable power station battery uses aluminum plastic film as the packaging material and requires heat encapsulation. The basic structure of the pouch cell lithium battery is similar to that of the cylindrical and square batteries, except that the pouch cell lithium battery is a liquid lithium-ion battery with a polymer shell and is structurally packaged in an aluminum-plastic film, usually consisting of three layers.

The nylon layer ensures the shape of the aluminum-plastic film, the Al layer prevents water infiltration, and the PP (polypropylene) layer effectively prevents the internal electrolyte from contacting the Al layer to avoid corrosion of the Al layer.

The packaging material and structure of pouch cell battery make it have a series of advantages, such as good safety performance. Pouch cell battery adopts aluminum-plastic film packaging in its structure, and in case of safety problems, pouch cell battery will generally bulge and crack instead of exploding like steel or aluminum shell battery cells; light weight, which can reduce the burden of the car; flexible design, which can change the shape of the form at will.

The disadvantages of this kind of portable energy storage battery are poor consistency, high cost, easy leakage, and the aluminum-plastic film looks simple, but how to combine the three layers of material evenly and firmly is not easy, and now the good quality aluminum-plastic film is basically dependent on imports from other countries, the quality of China’s domestic aluminum-plastic film still needs to be improved.

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