What are the differences between polymer lithium battery and lithium iron phosphate battery
1、 Overview of polymer lithium battery
Polymer lithium battery generally refers to polymer lithium ion battery.
According to the different electrolyte materials used in lithium-ion batteries, lithium-ion batteries are divided into liquid lithium-ion batteries (LIB), polymer lithium-ion batteries (PLB) or plastic lithium-ion batteries (PLB). The positive and negative materials used in polymer lithium-ion batteries are the same as those of liquid lithium ions. The positive materials are divided into lithium cobalt oxide, lithium manganate, ternary materials and lithium iron phosphate materials. The negative electrode is graphite, and the working principle of the battery is basically the same. Their main difference lies in the different electrolytes. Liquid lithium ion batteries use liquid electrolytes. Polymer lithium ion batteries are replaced by solid polymer electrolytes. The polymer can be either "dry" or "colloidal".
Polymer lithium battery classification:
Solids:
Solid polymer electrolyte lithium ion battery electrolyte is a mixture of polymer and salt. This battery has high ionic conductivity at room temperature and can be used at room temperature.
Gel: Set & Match:
Gel polymer electrolyte lithium ion battery, that is, adding plasticizers and other additives in solid polymer electrolyte, improves ionic conductivity and enables the battery to be used at room temperature.
Polymer:
Because the solid electrolyte is used to replace the liquid electrolyte, compared with the liquid lithium-ion battery, the polymer lithium-ion battery has the advantages of thinning, arbitrary area and arbitrary shape. Therefore, the battery shell can be made of aluminum-plastic composite film, so as to improve the specific capacity of the whole battery; Polymer lithium-ion batteries can also use polymers as cathode materials, and its mass specific energy will be more than 20% higher than the current liquid lithium-ion batteries. Polymer lithium-ion battery has the characteristics of miniaturization, thinness and lightweight. Therefore, the market share of polymer batteries will gradually increase.
Principle of polymer lithium battery:
At present, lithium-ion batteries include liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (PLB). Among them, liquid lithium ion battery refers to the secondary battery with Li + embedded compound as positive and negative electrodes. The positive electrode adopts lithium compound LiCoO2, LiNiO2 or LiMn2O4, and the negative electrode adopts lithium carbon interlayer compound lixc6. The typical battery system is:
The principle of polymer lithium-ion battery is the same as that of liquid lithium, and the main difference is that the electrolyte is different from that of liquid lithium. The main structure of the battery includes three elements: positive electrode, negative electrode and electrolyte. The so-called polymer lithium-ion battery means that at least one or more of the three main structures use polymer materials as the main battery system. In the currently developed polymer lithium-ion battery system, polymer materials are mainly used in cathode and electrolyte. The cathode materials include conductive polymer or inorganic compounds used in general lithium-ion batteries. The electrolyte can use solid or colloidal polymer electrolyte or organic electrolyte. General lithium-ion technology uses liquid or colloidal electrolyte. Therefore, strong secondary packaging is required to contain combustible active components, which increases the weight, It also limits the flexibility of size.
The new generation of polymer lithium-ion batteries can be thin in shape (ATL batteries can be as thin as 0.5mm, corresponding to the thickness of a card), arbitrary in area and arbitrary in shape, which greatly improves the flexibility of battery modeling design, so that they can be made into batteries of any shape and capacity according to product requirements, It provides 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 battery is 20% higher than that of current general lithium-ion battery, and its capacity, and environmental protection performance are better than lithium-ion battery.
Advantages and disadvantages of polymer lithium battery:
1. The working voltage of single battery is as high as 3.6V ~ 3.8V, which is much higher than the 1.2V voltage of Ni MH and Ni Cd batteries.
2. Large capacity density, which is 1.5 ~ 2.5 times or higher than that of Ni MH battery or Ni Cd battery.
3. The self discharge is small, and its capacity loss is also small after being placed for a long time.
4. Long service life, and its cycle life can reach more than 500 times under normal use.
5. Without memory effect, it is not necessary to empty the remaining power before charging, which is convenient to use.
6. Good safety performance
Polymer lithium battery adopts aluminum-plastic flexible packaging in structure, which is different from the metal shell of liquid cell. In case of potential safety hazards, the liquid cell is easy to explode, while the polymer cell will only inflate at most.
7. The thickness is small and can be made thinner
Ultra thin, batteries can be assembled into credit cards. Ordinary liquid lithium battery adopts the method of customizing the shell first and then plugging the positive and negative materials. The thickness is less than 3.6mm, which has a technical bottleneck. The polymer cell does not have this problem. The thickness can be less than 1mm, which meets the current demand direction of mobile phones.
8. Light weight
Batteries using polymer electrolyte do not need a metal shell as a protective outer package. The weight of polymer battery is 40% lighter than that of steel shell lithium battery with the same capacity specification and 20% lighter than that of aluminum shell battery.
9. Large capacity
The capacity of polymer battery is 10 ~ 15% higher than that of steel shell battery with the same size and specification, and 5 ~ 10% higher than that of aluminum shell battery. It has become the first choice for color screen mobile phones and MMS mobile phones. Now, most of the new color screens and MMS Mobile phones on the market also use polymer cells.
10. Small internal resistance
The internal resistance of polymer cell is smaller than that of general liquid cell. At present, the internal resistance of domestic polymer cell can even be less than 35m Ω, which greatly reduces the self power consumption of battery and prolongs the standby time of mobile phone, which can fully reach the level in line with international standards. This polymer lithium battery supporting large discharge current is an ideal choice for remote control model and has become the most promising product to replace Ni MH battery.
11. The shape can be customized
Manufacturers are not limited to standard shapes and can economically make appropriate sizes. Polymer batteries can increase or decrease the cell thickness according to the needs of customers, and develop new cell models with low price and short mold opening cycle. Some can even be customized according to the shape of mobile phones, so as to make full use of the battery shell space and improve the battery capacity.
12. Good discharge characteristics
Polymer battery adopts colloidal electrolyte. Compared with liquid electrolyte, colloidal electrolyte has stable discharge characteristics and higher discharge platform.
13. The design of protective plate is simple
Due to the use of polymer materials, the cell does not fire and explode, and the cell itself has sufficient safety. Therefore, the protection circuit design of polymer battery can consider omitting PTC and fuse, so as to save the battery cost.
Disadvantages:
1. High battery cost and difficult purification of electrolyte system.
2. It is necessary to protect the line control. Overcharge or over discharge will destroy the reversibility of chemicals in the battery, which will seriously affect the service life of the battery.
2、 Overview of lithium iron phosphate battery
Lithium iron phosphate battery refers to a lithium-ion battery using lithium iron phosphate as the cathode material. The cathode materials of lithium-ion batteries mainly include lithium cobalt oxide, lithium manganate, lithium nickel oxide, ternary materials, lithium iron phosphate, etc. Lithium cobalt oxide is the cathode material used in most lithium-ion batteries.
