Comparison of Lithium-ion and Lithium-Polymer Batteries

First, structurally, lithium-polymer batteries should be called lithium-ion polymer batteries. In this way, lithium-polymer batteries are actually a type of lithium-ion battery. The biggest difference between the two is that the electrolytes used inside are different. Lithium-ion batteries use liquid electrolytes, while polymer lithium-ion batteries are replaced by solid polymer electrolytes. This polymer can be solid. It can also be semi-solid(colloidal).

Cylinder lithium ion battery

Second, in terms of appearance, most of the mobile power sources currently sold on the market use cylindrical(ie, 18650) lithium ion batteries or massive lithium polymer batteries. So when we select a mobile power source, if the outer package of the product does not specify the type of core used, then it is possible to simply understand the type of battery used internally by the thickness of the product itself.

Lithium-ion batteries are improved products of lithium batteries. Because the chemical properties of lithium metals are very lively, early lithium batteries often burn during use. In order to inhibit the active chemical properties of lithium metals, people have greatly enhanced the safety factor of early lithium batteries by adding cobalt, manganese and other metal materials to the positive electrode materials of lithium batteries.

Embedding and deem bedding of lithium-ion batteries

The charging and discharge of lithium-ion batteries can be accomplished by embedding and deem bedding. During discharge, lithium ions are removed from the positive electrode material to the electrolyte, and then enter the negative electrode material like water enters the sponge. This process is called deem bedding. In the charging state, this process is the opposite, called embedding. In the figure below, Zuowei's lithium battery is embedded and the right is deem bedded.

The most common 18650 battery

It can be said that after many years of development, the technology of lithium-ion batteries has been relatively mature, and mass production has made its manufacturing cost very low. So lithium-ion batteries are more expensive than lithium-polymer batteries. This is why most laptops and other devices now use this type of core.

18650 battery structure

Since lithium ions using liquid electrolytes can cause their internal pressure to soar under overcharge(overcharge), this 18650 battery is usually equipped with a safety valve at the top to avoid an explosion of the sealed metal shell. When the internal pressure of the battery is too large, the top relief valve will automatically pop up to reduce the pressure. However, when the relief valve pops up, the lithium ion leaked inside the battery will still catch fire due to contact with oxygen in the air.

Therefore, for electronic products that use this lithium ion core, there are very high requirements for charging and discharging protection ICs inside them. However, with the development of lithium-ion batteries over the years, both the design of the battery itself and the technical level of various protection ICs are very mature, as long as we can use them correctly and avoid the phenomenon of batteries being punctured by hard objects during daily use. The 18650 core is still very safe, otherwise, most laptops on the market will not use this type of battery.

Compared to lithium-ion batteries using liquid electrolytes, lithium-polymer batteries using solid polymer electrolytes have the characteristics of ultra-thinning in shape, with a theoretical minimum thickness of up to 0.5 mm, as well as arbitrary shape and arbitrary area. It greatly improves the flexibility of the battery shape, so that it can be better made into a new generation of lithium batteries of any shape and capacity.

Lithium polymer battery

In addition, lithium-polymer batteries using solid polymer electrolytes have a higher energy density than ordinary lithium-ion batteries, that is, lithium-polymer batteries have lighter weight and higher capacity on the same volume premise. Advantages such as.

Lithium polymer batteries are thinner

If in a strict sense, lithium-polymer batteries are the same as lithium-ion batteries that use liquid electrolytes because of their positive, negative, and electrolyte working principles, the only difference is the difference between the diaphragm and the packaging material. Therefore, fundamentally, Lithium-polymer batteries are also a type of lithium ion battery.

Therefore, for lithium ion batteries with different packaging forms, they have the following characteristics:

Steel shell lithium ion battery:

Common 18650 batteries using steel shells have a high safety factor, production technology has become very mature, and the price is cheaper than polymer batteries, occupying most of the lithium battery market share, the most common in laptop batteries.

Lithium-ion battery(polymer battery):

With higher energy density, better safety performance, and arbitrary shapes, it has become the preferred core for most mainstream digital products, but the price is still high compared to steel-shell lithium-ion batteries.

Summarizing: In fact, whether it is a steel shell lithium ion battery or a soft package lithium ion battery, its performance in safety performance is very good. After all, the current production technology of lithium ion batteries is very mature. As long as we avoid the occurrence of high temperatures, short circuits, overcharging, piercing, etc. during daily use, we can avoid the occurrence of accidents such as "explosion" and fire. For what we call lithium-ion batteries and lithium-polymer batteries, both have their own advantages and disadvantages. If you prefer the price of the product, choose the 18650 battery. If you prefer the appearance and volume of the mobile power supply. Then the more expensive lithium polymer core is the first choice.

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