Lithium Ion And Lithium Polymer Batteries

Dec. 25, 2020

Lithium Ion And Lithium Polymer Batteries

Lithium ion (Li-ion) batteries have always been the preferred power source for smartphones and various other portable devices. However, most smart phones now usually use lithium polymer (Li-poly) batteries, which are gradually replacing lithium-ion batteries as the mainstream. However, what caused this trend to appear? What is the difference between lithium ion batteries and lithium polymer batteries, and what are their advantages and disadvantages are what we should know.

Before clarifying their differences and advantages and disadvantages, we must first understand how they work. Lithium-ion batteries are the main force in the industry. The development of this technology began in 1912, but it was not popularized until it was adopted by Sony in 1991. Since then, lithium-ion batteries have provided power for various small devices, such as portable cameras, music players, and smart phones.

Part of the reason why Li-ion batteries are so successful is that they have a very high energy density, do not have a "memory effect" like the previous battery technology (that is, batteries become more difficult to charge over time), and their production costs are relatively cheap.

Lithium-ion batteries consist of two positive and negative electrodes separated by a liquid chemical electrolyte such as ethylene carbonate or diethyl carbonate. The chemical composition of this battery limits its shape to a rectangular shape. The capacity of lithium-ion batteries will decrease with the charging cycle, and will even discharge when not in use, which is not ideal. To make matters worse, the chemical electrolyte becomes unstable at extreme temperatures or if it is punctured, leading to "thermal runaway" and fire. However, this situation is very rare, because the electronic controller usually adjusts the charging and discharging power to prevent the battery from overheating.

Lithium polymer battery technology is more advanced than lithium ion batteries. It didn't appear until the 1970s, and has only been installed in smartphones in recent years. For example, Samsung switched to lithium polymer in the Galaxy S20 series, while other manufacturers used the technology earlier. And Samsung used lithium-ion back on the Galaxy Note 20 series.

Lithium polymer technology also uses positive and negative electrodes, but uses a dry solid, porous chemical or gel electrolyte instead of a liquid. Therefore, the polymer battery can provide a lower profile, flexible and more robust design, and the possibility of electrolyte leakage causing thermal runaway is lower. In short, they are safer.

A major disadvantage of this technology is that the manufacturing cost is significantly higher. The life cycle of lithium polymer is also shorter, and the battery can store less energy than a lithium-ion battery of the same size. These batteries still need to rely on protection circuits to keep the voltage running within a safe range.

Both types of batteries have their advantages and disadvantages. Generally speaking, lithium-ion batteries have the largest capacity and are cheaper. The disadvantage of lithium-ion batteries is that they will gradually self-discharge, but for mobile phones that have been turned on, this is not too important, and the possibility of safety issues is small, but not zero.

In contrast, lithium polymer batteries are safer. This is particularly important in the era of rapid development of fast charging technology. The self-discharge of this kind of battery is also very low, so it will not lose a lot of electricity when you are not using it. However, this also brings a higher price, shorter life and lower capacity density. Although, the lightweight characteristics of lithium polymer batteries make the overall energy density of the battery better.

In general, due to the superior safety, versatility and weight properties of lithium polymer, it is widely used in high-end and mid-range devices, and Li-poly batteries are slowly replacing lithium ion in the smartphone industry.


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