What the differences between 18650 lithium ion battery and Lithium polymer battery

18650 battery is cylinder with liquid inside. Due to the battery design and materials, 18650 battery is suitable for large current, and is nearly used in all the laptop and electric car. Only Ultrabook doesn’t use 18650 battery but lithium polymer battery, especially tablet, because of energy conservation. Given that digital camera has flashlight function, it can only apply 18650 battery with smaller size for high voltage and high constant current.

The advantages of lithium polymer battery are small size and large capacity. But it has shorter cycle life than 18650 battery. Due to different design and materials, some batteries has liquid inside, some are dry or colloid, and the performance is not as good as that of 18650 battery when discharge under large current. If your electronic devices need battery with large capacity but small size, especially mobile phone and tablet, you can choose polymer battery.

As the 18650 battery has advantages of high energy density and discharging under large current, so-called polymer battery is the lithium ion battery using polymer as electrolyte, which can be divided into semi-polymer and whole-polymer. Semi-polymer battery means covering a layer of polymer (it tends to be PVDF) on separator to make the adhesive force of the battery stronger, so that the battery becomes more tough. The electrolyte is still liquid. The whole-polymer battery refers to using polymer to make gel network inside the cell, and then inject electrolyte. Whole-polymer battery still needs a little liquid electrolyte, which apparently upgrades the safety performance of lithium ion battery. It is known that only SONY has whole-polymer battery in mass production at present.

On the other hand, polymer battery is lithium ion battery using aluminum plastic film as external package, which is so-called pouch battery. The package film is made by three layers materials. They are PP, AI and nylon. Because PP and nylon are polymer, this kind of battery is named polymer battery.

Lower price

The global price of 18650 battery is around 1USD/pcs. It costs about 3RMB/Ah calculating by 2Ah. As for the price of polymer lithium ion battery, the battery produced by the low-end pirated factory is 4RMB/Ah, medium-end is 5~7RMB/Ah, while mid-to-high end is over 7RMB/Ah. The battery of ATL and Lision will cost at least 10RMB/Ah, and they won’t accept small order.

No customization

SONY commits to produce lithium ion battery as alkaline battery with industrial standard, just like AA battery and AAA battery, which are unified all over the world. However, because one of the biggest advantages of lithium ion battery is designing the appearance according to customer’ requirement, there won’t be a unified standard. All the lithium ion batteries are design by customer’s requirements except 18650 battery, the only one standard size of lithium ion battery.

Poor safety performance

It is known that lithium ion battery will have severe chemical reaction inside and produce a large amount of gas under extreme circumstance (such overcharging, high temperature, etc.). 18650 battery has metal shell with certain strength. When the pressure inside the battery is up to a certain value, it may lead to dangerous accident.

This is why protect the testing room seriously and make sure nobody in when test the 18650 battery. There is no such a question for polymer battery. Even under extreme circumstance, it won’t explode but break under high pressure due to its weak strength of package film. The worst result is burning, so the safety performance of polymer battery is better than 18650 battery.

Low energy density

Normally, the capacity of 18650 battery can reach 2200 mAh or so, so that the energy density is around 500Wh/L, while the present energy density of polymer battery is nearly 600Wh/L.

Polymer battery also has its shortcoming, which has higher cost, including R&D cost because it provides custom service. Besides, the fixtures during manufacturing process are not standard parts due to its diversified appearance and variety. Flexible design leads to poor versatility. We need to design another fixture for customer even for distinction of 1mm.

The application of 18650 battery

Lithium ion secondary battery is applied in energy battery industry due to its outstanding performance. As the continuous development, lithium ion secondary battery is widely used in our daily life. Rechargeable battery is more and more popular for the consumers. Paying attention to energy battery industry and knowing more about battery can helps us a lot. Recently, 18650 battery is widely used in following areas.

Energy storage

It is widely used in power supply of base station, clean energy storage, energy storage of power grid, household PV system, etc.

Power category

It mainly refers to electrical vehicles, electric bicycle, new-energy vehicles, etc.

Digital category

Mobile phone, tablet, laptop, electronic toys, MP3/MP4, earphone, power bank, model airplane, portable power source, etc.