Lithium polymer batteries, also known as high-molecular lithium batteries, are a type of chemical battery. Compared to previous batteries, they are characterized by high energy density, miniaturization, and lightweight design. Lithium polymer batteries are also ultra-thin, allowing them to be manufactured in various shapes and capacities to meet the needs of different products; theoretically, the minimum thickness can reach 0.5mm.
The difference between lithium-ion batteries and lithium polymer batteries
The positive and negative electrode materials used in polymer lithium-ion batteries are the same as those in liquid lithium-ion batteries. The positive electrode materials are divided into lithium cobalt oxide, lithium manganese oxide, ternary materials, and lithium iron phosphate materials, while the negative electrode is graphite. The working principle of the batteries is also basically the same. Their main difference lies in the electrolyte. Liquid lithium-ion batteries use liquid electrolytes, while polymer lithium-ion batteries use solid polymer electrolytes instead. This polymer can be in a "dry" state or a "gel" state, and currently most use polymer gel electrolytes.
Which is better, lithium polymer batteries or lithium-ion batteries?
Lithium polymer batteries are better. They are an upgraded version of lithium-ion batteries, offering advantages such as larger capacity, smaller (thinner) size, and greater safety (no explosion). However, due to the time required for the entire industry chain to be upgraded, their manufacturing cost is currently relatively high, and they are only used in high-end digital products (such as ultra-thin laptops).
The advantages of lithium polymer batteries are mainly as follows:
1. The working voltage of a single lithium polymer battery cell is as high as 3.6V~3.8V, which is much higher than the 1.2V voltage of nickel-metal hydride and nickel-cadmium batteries.
2. Lithium polymer batteries have a high capacity density, which is 1.5 to 2.5 times, or even higher, than that of nickel-metal hydride or nickel-cadmium batteries.
3. Lithium polymer batteries have low self-discharge and minimal capacity loss even after prolonged storage.
4. Lithium polymer batteries have a long lifespan; under normal use, their cycle life can reach more than 500 times.
5. Lithium polymer batteries have no memory effect, so there is no need to completely discharge the remaining power before charging, making them convenient to use.
6. Good safety performance: Polymer lithium batteries use aluminum-plastic soft packaging in their structure, which is different from the metal shell of liquid cells. In the event of a safety hazard, liquid cells are prone to explosion, while polymer cells will at most bulge.
7. Thinner profile, allowing for even thinner designs: Lithium polymer batteries are ultra-thin, capable of being assembled into a credit card. Traditional liquid lithium batteries use a method of first customizing the casing and then inserting the positive and negative electrode materials, which presents a technical bottleneck in achieving a thickness of 3-6mm or less. Polymer cells do not have this problem, and their thickness can be reduced to less than 1mm, meeting current mobile phone demand trends.
8. Lightweight
Lithium polymer batteries, which use polymer electrolytes, do not require a metal casing for protection. Polymer batteries are 40% lighter than steel-cased lithium batteries of the same capacity and 20% lighter than aluminum-cased batteries.
9. Large capacity
Polymer lithium batteries have 10-15% higher capacity than steel-cased batteries of the same size and 5-10% higher capacity than aluminum-cased batteries, making them the preferred choice for color screen and MMS phones. Most new color screen and MMS phones on the market now use polymer cells.
10. Low internal resistance
Polymer lithium-ion battery cells have lower internal resistance than conventional liquid-state batteries. Currently, the internal resistance of domestically produced polymer cells can even be below 35mΩ, significantly reducing battery self-discharge and extending mobile phone standby time, fully meeting international standards. This type of polymer lithium-ion battery, which supports high discharge current, is also an ideal choice for remote control models, becoming the most promising replacement for nickel-metal hydride batteries.
11. Shape can be customized
Manufacturers are not limited to standard shapes and can economically produce batteries of suitable sizes. Polymer lithium batteries can increase or decrease cell thickness according to customer needs, develop new cell models, are inexpensive, have short mold opening cycles, and some can even be custom-made to fit the shape of the phone to make full use of the battery casing space and increase battery capacity.
12. Excellent discharge characteristics
Polymer lithium batteries use gel electrolytes, which have more stable discharge characteristics and a higher discharge platform compared to liquid electrolytes.
13. The protection board has a simple design.
Because polymer materials are used, polymer lithium battery cells do not catch fire or explode, and the cells themselves have sufficient safety. Therefore, the protection circuit design of polymer batteries can omit PTC and fuses, thereby saving battery costs.
