Li-ion Battery Vs. Li-polymer: Which Works Better For Your External Battery Charger

Just like a car’s fueltank and transmission, Li-ion or Li-polymer battery cell is the key of a portable charger and directly determines it’s good or not. But it has been know that most consumers cannot distinguish them and make a right buying decision, as they generally can not be reflected in the specification label. In this article we explore their basic relationship and differences.


The Lithium-ion Battery

The first commercialized lithium-ion battery began in 1991 under Sony Corporation and then quickly followed by other manufacturers. As its energy density, load characteristic, and discharge behavior are reasonably good.

Lithium-ion is a low maintenance battery, an advantage that most other chemistries cannot claim. There is no memory and no scheduled cycling is required to prolong the battery’s life. In addition, the self-discharge is less than half compared to nickel-cadmium, making lithium-ion well suited for modern fuel gauge applications.

Lithium-ion has its drawbacks. It is fragile and requires a protection circuit to maintain safe operation.The cell temperature is monitored to prevent temperature extremes. Aging is another problem and many manufacturers remain silent about this issue. The battery frequently fails after two or three years.

The most economical lithium-ion battery in terms of cost-to-energy ratio is the cylindrical 18650 (size is 18mm x 65.2mm). This cell is used for mobile computing and other applications that do not demand ultra-thin geometry, now available in more than 60% of the external battery charger that bulky and wrapped in metal case.

Main advantages: mature technology, wide range of applications, compact size.

Main disadvantages: about 300 times cycle life, low security, anti-overcharge poor, not suitable for high-rate charge and discharge.


The Lithium Polymer Battery

The Lithium-polymer differs from other battery systems in the type of electrolyte used. The original design, dating back to the 1970s, uses a solid (dry) polymer electrolyte that has a poor conductivity, and the battery must be heated to 50–60°C to enable current flow, so that it is unsuitable for portable applications. To compromise, some gelled electrolyte has been added. All Li-ion polymer cells today incorporate a micro porous separator with moisture. The correct term is “Lithium-ion polymer” (Li-polymer for short).

Then, what is the difference between a normal Li‑ion and Li‑polymer?

As far as the user is concerned, they both use identical cathode and anode material and contain a similar amount of electrolyte. Although the characteristics and performance of the two systems are alike, the gelled electrolyte of Li‑polymer becomes the catalyst that enhances the electrical conductivity. Li-polymer offers slightly higher specific energy and can be made thinner than conventional Li-ion, but the manufacturing cost increases by 10–30 percent. Despite the cost disadvantage, the market share of Li-polymer is growing.

Li-polymer cells also come in a flexible foil-type case (polymer laminate or pouch cell), while a standard Li-ion needs a rigid case that increases the weight by more than 20 percent. Furthermore, the Li-polymer battery can be made into any shape, fitting neatly into stylish cell phones and laptops to make them smaller, thinner and lighter, as well as Kinkoo Infinite One 8000mAh and Infinite Nova 10500 Portable External Battery Charger.   

Main advantages: Volume diversity, lightweight; the use of a very wide range, not an explosion, high safety factor.

Main disadvantage: about 500 times cycle life, higher prices, not suitable for high-rate charge and discharge.


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