Lithium-ion and lithium-polymer batteries really explode?

When we choose mobile power, we often see two different types of batteries, lithium ion and lithium polymer, in the product packaging or brochure. So what are the differences between them? For some consumers, is lithium polymer battery really better than lithium ion battery? With these questions, today I will give you a detailed introduction to the advantages and disadvantages of these two batteries in terms of price, performance and security.

First of all, from the structural point of view, the full name of the lithium polymer battery should be a lithium ion polymer battery, so it seems that the lithium polymer battery is actually a kind of lithium ion battery. The biggest difference between the two is that the electrolyte used in the interior is different. The lithium ion battery uses a liquid electrolyte, while the polymer lithium ion battery is replaced by a solid polymer electrolyte. The polymer can be solid or It is semi-solid (gelatinous).

Cylindrical lithium ion battery

Secondly, in terms of appearance, most of the mobile power sources currently on the market use a cylindrical (18650) lithium ion battery or a block lithium polymer battery, therefore, when we select the mobile power supply, if the product packaging does not specifically indicate the type of battery used, then simply by the thickness of the product itself, a general understanding of the type of battery used inside.

Lithium-ion batteries are an improved product of lithium batteries. Due to the very active chemical properties of lithium metal, early lithium batteries often burn when used. In order to suppress the active chemical properties of lithium metal, people added the other metal materials such as cobalt and manganese to the positive electrode material of the lithium battery, which greatly enhanced the safety factor of the early lithium battery.

Embedding and deintercalation of lithium ion batteries

Lithium-ion battery charging and discharging can be completed by two processes of embedding and deintercalation. During discharge, lithium ions are removed from the positive electrode material to the electrolyte, and then enter the negative electrode material like water into the sponge. This process is called for deintercalation. In the state of charge, this process is reversed, called in-embedded. In the figure above, the left is the process of inserting the lithium battery, and the right is the de-embedding process.

The most common 18650 battery

It can be said that after years of development, the technology of lithium-ion batteries is relatively mature, and the mass production has made its manufacturing cost very low. Therefore, lithium-ion batteries are more advantageous in price than lithium polymer batteries. This is why it is used in most laptops and other devices.

18650 battery structure

Since lithium ions using a liquid electrolyte will increase their internal pressure in the case of overcharging (overcharging), in order to avoid explosion of the sealed metal casing, the 18650 battery is usually equipped with a safety at the top. Valve, when the internal pressure of the battery is too large, the top safety valve will automatically pop out to play the role of decompression. However, when the safety valve is ejected, the lithium ions leaking inside the battery may still be ignited due to contact with oxygen in the air.

Therefore, for electronic products using such lithium ion batteries, there are very high requirements on their internal charge and discharge protection ICs. However, with the development of lithium-ion batteries for many years, both the design of the battery itself and the technical level of various protection ICs are very mature, as long as they can be used correctly in daily use and avoid the battery being pierced by hard objects. The phenomenon, 18650 batteries are still very safe, otherwise most notebooks on the market will not use this battery.

Compared with lithium ion batteries using liquid electrolytes, lithium polymer batteries using solid polymer electrolytes are ultra-thin in shape, with a theoretical minimum thickness of 0.5 mm, and any shape and arbitrary area. . The battery styling flexibility is greatly improved, so that a new generation of lithium batteries of any shape and capacity can be better formed.

Lithium polymer battery

In addition, a lithium polymer battery using a solid polymer electrolyte has a higher energy density than a conventional lithium ion battery, that is, a lithium polymer battery has a lighter weight and a larger volume under the same volume high capacity and other advantages.

Lithium polymer battery is lighter and thinner

In a strict sense, a lithium polymer battery is the same as a lithium ion battery using a liquid electrolyte in the positive electrode, the negative electrode, and the electrolyte. The only difference is the difference between the separator and the packaging material. Therefore, fundamentally speaking, Lithium polymer batteries are also a type of lithium ion batteries.

Therefore, for various lithium ion batteries of different package types, the following features are:

Steel shell lithium ion battery:

The common 18650 battery with steel shell has a high safety factor, the production technology is very mature, and the price is cheaper than the polymer battery, occupying the majority of the lithium battery market share, the most common in laptop batteries. .

Soft pack lithium ion battery (polymer battery):

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

Summary: In fact, whether it is a steel-shell lithium-ion battery or a soft-packed lithium-ion battery, the performance in safety performance is very good. After all, the current lithium-ion battery production technology is very mature, as long as it avoids high temperature and short circuit in daily use. The occurrence of overcharge, piercing, etc. can all avoid the occurrence of unexpected situations such as "explosions" and fires. For the lithium-ion battery and lithium polymer battery that we often say, both have their own advantages and disadvantages, if you are more inclined to the price/performance ratio of the product, choose 18650 battery, if you prefer the appearance of mobile power and Volume, then the price of a slightly more expensive lithium polymer battery is the first choice.

The page contains the contents of the machine translation.