1、 Overview of Polymer Lithium Batteries
Polymer lithium batteries generally refer to polymer lithium-ion batteries.
According to the different electrolyte materials used in lithium-ion batteries, lithium-ion batteries are divided into liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (pLB) or plastic lithium-ion batteries (pLB). The positive and negative electrode materials used in polymer lithium-ion batteries are the same as liquid lithium ions. The positive electrode materials are divided into lithium cobalt oxide, lithium manganese oxide, ternary materials, and lithium iron phosphate materials. The negative electrode is graphite, and the working principle of the battery is basically the same. The main difference between them lies in the different electrolytes. Liquid lithium ion batteries use liquid electrolytes, while polymer lithium ion batteries use solid polymer electrolytes instead. This polymer can be either "dry" or "colloidal". At present, most of them use polymer gel electrolytes.
Classification of polymer lithium batteries:
Solid:
Solid polymer electrolyte lithium-ion battery electrolyte is a mixture of polymer and salt, which has high ion conductivity at room temperature and can be used at room temperature.
Gel:
The gel polymer electrolyte lithium ion battery is to add plasticizers and other additives to the solid polymer electrolyte, so as to improve the ionic conductivity and enable the battery to be used at room temperature.
Polymer:
Due to the use of solid electrolytes instead of liquid electrolytes, polymer lithium-ion batteries have advantages such as thinning, arbitrary area, and arbitrary shape compared to liquid lithium-ion batteries. Therefore, aluminum-plastic composite films can be used to manufacture battery casings, thereby improving the specific capacity of the entire battery; Polymer lithium-ion batteries can also use polymers as positive electrode materials, which will increase their mass to energy ratio by more than 20% compared to current liquid lithium-ion batteries. Polymer Lithium ion batteries have the characteristics of miniaturization, thinning, and lightweighting. Therefore, polymer batteries will gradually increase their market share.
Principle of polymer lithium battery:
There are currently two types of lithium-ion batteries: liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (pLB). Among them, liquid lithium-ion batteries refer to secondary batteries with Li+embedded compounds as positive and negative electrodes. The positive electrode uses lithium compounds LiCoO2, LiNiO2 or LiMn2O4, and the negative electrode uses lithium carbon interlayer compound LixC6. A typical battery system is:
The principle of polymer lithium-ion batteries is the same as that of liquid lithium, with the main difference being the electrolyte. The main structure of a battery includes three elements: positive electrode, negative electrode, and electrolyte. The so-called polymer lithium-ion battery refers to a battery system that uses polymer materials as the main component in at least one or more of these three main constructions. In the currently developed polymer lithium-ion battery systems, polymer materials are mainly used for the positive electrode and electrolyte. Positive electrode materials include conductive polymer materials or inorganic compounds commonly used in lithium-ion batteries. Electrolytes can be solid or colloidal polymer electrolytes, or organic electrolytes. Generally, lithium-ion technology uses liquid or colloidal electrolytes, so sturdy secondary packaging is required to contain flammable active ingredients, which increases weight and limits size flexibility.
The new generation of polymer lithium-ion batteries can achieve thinning in shape (ATL batteries can be as thin as 0.5 millimeters, equivalent to the thickness of a card), arbitrary area, and arbitrary shape, greatly improving the flexibility of battery design. Therefore, they can be made into batteries of any shape and capacity to meet product requirements, providing equipment developers with some design flexibility and adaptability in power solutions to maximize their product performance. At the same time, the unit energy of polymer lithium-ion batteries has increased by 20% compared to current general lithium-ion batteries, and their capacity, environmental performance, and other aspects have improved to some extent compared to lithium-ion batteries.
Advantages and disadvantages of polymer lithium batteries: Advantages:
The working voltage of a single battery can reach up to 3.6V~3.8V, which is much higher than the 1.2V voltage of nickel hydrogen and nickel cadmium batteries.
2. It has a high capacity density, which is 1.5-2.5 times or higher than nickel hydrogen batteries or nickel cadmium batteries.
3. Small self discharge and minimal capacity loss after prolonged storage.
4. Long lifespan, with a normal cycle life of over 500 times.
5. There is no memory effect, so there is no need to empty the remaining battery before charging, making it easy to use.
6. Good safety performance
Polymer lithium batteries use aluminum-plastic flexible packaging in their structure, which is different from the metal casing of liquid batteries. In the event of a safety hazard, liquid batteries are prone to explosion, while polymer batteries can only inflate at most.
7. Small thickness, can be made thinner
Ultra thin, the battery can be assembled into a credit card. Ordinary liquid lithium batteries adopt the method of customizing the shell first, and then inserting positive and negative electrode materials. There is a technical bottleneck in achieving a thickness of less than 3.6mm, while polymer batteries do not have this problem. The thickness can be reduced to less than 1mm, which meets the current demand for mobile phones.
8. Lightweight
Batteries using polymer electrolytes do not require a metal shell as a protective outer packaging. Polymer batteries are 40% lighter than steel shell lithium batteries of the same capacity specification and 20% lighter than aluminum shell batteries.
9. Large capacity
Polymer batteries have a capacity 10-15% higher than steel shell batteries of the same size and specifications, and 5-10% higher than aluminum shell batteries, making them the preferred choice for color screen phones and MMS phones. Currently, most newly released color screen and MMS phones on the market also use polymer batteries.
10. Low internal resistance
The internal resistance of polymer battery cells is smaller than that of general liquid battery cells. Currently, the internal resistance of domestic polymer battery cells can even reach below 35m Ω, greatly reducing the self consumption of batteries and extending the standby time of mobile phones, which can fully reach the level of international standards. This polymer lithium battery that supports high discharge current is an ideal choice for remote control models and has become the most promising alternative to nickel hydrogen batteries.
11. Shape can be customized
Manufacturers are not limited to standard shapes and can economically produce suitable sizes. Polymer batteries can increase or decrease the thickness of battery cells according to customer needs, develop new battery cell models, be inexpensive, have short mold cycles, and some can even be customized according to the shape of the phone to fully utilize the space of the battery casing and increase battery capacity.
12. Excellent discharge characteristics
Polymer batteries use colloidal electrolytes, which have smooth discharge characteristics and higher discharge platforms compared to liquid electrolytes.
13. Simple design of protective board
Due to the use of polymer materials, the battery cells do not ignite or explode, and have sufficient safety. Therefore, the protection circuit design of polymer batteries can consider omitting pTC and fuses to save battery costs.
Disadvantages:
1. High battery costs and difficulty in purifying electrolyte systems.
2. It is necessary to protect the circuit control, as overcharging or overdischarging can damage the reversibility of the chemical substances inside the battery, thereby seriously affecting the battery's lifespan.
2、 Overview of lithium iron phosphate batteries
Lithium iron phosphate battery refers to a lithium-ion battery that uses lithium iron phosphate as the positive electrode material. The positive electrode materials of lithium-ion batteries mainly include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, ternary materials, lithium iron phosphate, etc. Lithium cobalt oxide is currently the majority of positive electrode materials used in lithium-ion batteries.
